# Review: Canon RF 16mm f/2.8 STM by Christopher Frost



## Canon Rumors Guy (Oct 26, 2021)

> One of my favourite lens reviewers Christopher Frost has completed his review of the brand new Canon RF 16mm f/2.8 STM.
> The review showcases all of the strengths and weaknesses of Canon’s new $300 prime lens for the RF mount. Keep realistic expectations for this little lens, it is $300 after all.
> Interestingly, you cannot turn off distortion correction in your EOS R body with this lens. Canon has decided to use the camera body to make up for optical weaknesses, which is probably just fine for most applications.
> *Canon RF 16mm f/2.8 STM Key Features*
> ...



Continue reading...


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## victorshikhman (Oct 26, 2021)

> Canon has decided to use the camera body to make up for optical weaknesses



Wasn't the RF mount supposed to allow easier engineering of better designs without these optical weaknesses? Watching this review, the way the focus sounds like the original nifty fifty... It feels like they just slapped this together for lowest possible cost.

Meanwhile, I'm kicking myself. Two years ago I had a chance to purchase a 24-70 F/4 for $550, and I thought... meh, that's kinda pricey. Now it's going for $1200 on ebay from reputable places. The 16-35 F/4 is also skyrocketing. Maybe supply disruptions are a part of this, but there's still so much demand in good EF lenses, and they're optically no worse than the RF versions. Is Canon leaving money on the table?


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## Andy Westwood (Oct 26, 2021)

Christopher is also one of my favourite lens reviewers along with Dustin Abbott. This review is kind of what I was expecting on this compact cheap lens, no wow’s but still a nice little bit of glass.

My pre-order is in-store now, I’ll be picking it up on Thursday this week. I didn’t expect this lens to compete with my Sigma 14-24 f/2.8 but for a cheap compact wide lens that you’ll hardly know you have on your camera and isn’t going to put your back out when using it, I can live with its spots and pimples.


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## neuroanatomist (Oct 26, 2021)

victorshikhman said:


> Wasn't the RF mount supposed to allow easier engineering of better designs without these optical weaknesses? Watching this review, the way the focus sounds like the original nifty fifty... It feels like they just slapped this together for lowest possible cost.


Well, $300 is a pretty low cost, relatively speaking. I really do think Canon is planning on launching a sub-$800 FF EOS R, and the RP is now $1000. Having an inexpensive FF body with only costly lenses for it is not a recipe for success. But consider – the combination of the RF 16/2.8, RF 24-105 non-L, and RF 100-400 gives a user a very large focal range for a $1350 outlay.


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## InchMetric (Oct 26, 2021)

victorshikhman said:


> Wasn't the RF mount supposed to allow easier engineering of better designs without these optical weaknesses? Watching this review, the way the focus sounds like the original nifty fifty... It feels like they just slapped this together for lowest possible cost.


No. They make some very fine and expensive lenses for the nerds who are allergic to corrections, and they make some lenses that perform nicely as an engineered system for people who want to take great pictures with a light and inexpensive lens.

Then again, those $100,000 Mercedes S-class sedans drive like crap with all the computerized traction control systems turned off. Can't Mercedes design a decent car anymore? I also hear the U.S. Air Force has some planes that won't even fly without computers ensuring stability. Talk about a step backward! Why can't they all be as smart as me and design things right?


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## gbc (Oct 26, 2021)

This was the first lens I ever pre-ordered as soon as it was available and didn't think twice. Got it last week and took it to a concert, and I am pretty pleased. I've been using a Tokina 11-16 2.8 for about 10 years now, even as I moved to full frame and could only use it as a 16mm prime for the most part, so I've been on the lookout for a replacement for quite some time. Not having to use the RF adapter and having a 16mm that is 1/3 the size and maybe 1/5 the weight... it's a revelation. And the images so far have been pretty good. Like the review says, it's dead sharp in the middle, which for my purposes is all I need, since i use it in situations when the subject is up close and I just want a wide frame. for $300 this is a no brainer.


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## vangelismm (Oct 26, 2021)

the glass it is not enough to 16mm...


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## AJ (Oct 26, 2021)

There are huge big heavy expensive super-corrected lenses, and then there are small, simple lenses like this 16/2.8. There is a purpose for each. The 16/2.8 will be a perfect travel/backpacking lens. I will be getting one. The pre-corrected barrel distortion doesn't bother me at all. I think it is quite a clever trick actually. If it helps reduce size, weight and cost, then I'm all for it.
I do hope Canon develops more lenses in this spirit. For example, it'd be nice if they made an R-mount version of the classic 50/1.4 with double-gauss design rather than the big heavy Sigma 50/1.4 versions. All that would be needed is a modern AF motor, improved coatings, and perhaps a tweak to the optical formula. Yes I know we already have a 50/1.8 in R mount but 1.4 would be nice.


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## tbgtomcom (Oct 26, 2021)

I could see this lens being a hit with bloggers.


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## AJ (Oct 26, 2021)

neuroanatomist said:


> Well, $300 is a pretty low cost, relatively speaking. I really do think Canon is planning on launching a sub-$800 FF EOS R, and the RP is now $1000. Having an inexpensive FF body with only costly lenses for it is not a recipe for success. But consider – the combination of the RF 16/2.8, RF 24-105 non-L, and RF 100-400 gives a user a very large focal range for a $1350 outlay.


Let's call it the unholy trinity, shall we? Or evil trinity?


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## entoman (Oct 26, 2021)

victorshikhman said:


> Wasn't the RF mount supposed to allow easier engineering of better designs without these optical weaknesses?


Yes, and we’ve already seen plenty of evidence of this with lenses such as the 28-70mm F2 and the 100mm macro. But they are expensive optics, and when the original R was launched there were endless complaints that Canon didn’t cater for the budget end of the market.

Now they have a near-complete set of exotic L glass AND an excellent selection of budget glass covering everything from 16mm to 800mm. And some people still complain…



victorshikhman said:


> Watching this review, the way the focus sounds like the original nifty fifty... It feels like they just slapped this together for lowest possible cost.


This is a $300 lens, it’s pretty unrealistic to expect it to be as smooth and quiet in operation as an L lens.

It’s designed to be a *cheap* and pocketable lens that can be carried at all times and takes up virtually no space in a camera bag.

Sure, they could easily have put a few more elements in the lens and avoided the need for computational aberration correction, they could also have put in a better focus motor, and included optical stabilisation. But if they did it would weigh 5 times as much and cost 5 times more.


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## stevelee (Oct 26, 2021)

InchMetric said:


> No. They make some very fine and expensive lenses for the nerds who are allergic to corrections, and they make some lenses that perform nicely as an engineered system for people who want to take great pictures with a light and inexpensive lens.
> 
> Then again, those $100,000 Mercedes S-class sedans drive like crap with all the computerized traction control systems turned off. Can't Mercedes design a decent car anymore? I also hear the U.S. Air Force has some planes that won't even fly without computers ensuring stability. Talk about a step backward! Why can't they all be as smart as me and design things right?


My Audi at half that price has the four wheels under so much computer control that I don’t think you can turn much of it off, mostly just for driving in ice or something. The feel that the computer control gives when going over hilly, twisty roads is great, as if I knew what I am doing. You can set various components of that control to suit for a custom setup, and not just a choice for everything at once between Sport and regular Drive modes.

I am glad that my G5X II doesn’t have the extra pound of glass it would take to correct the little lens to an acceptable level without software corrections. I bet the owners of the little 16mm lens will feel the same way.


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## mccasi (Oct 26, 2021)

I have the lens too and I’m quite happy for my use cases.


For selfie I don’t care about corner sharpness, but all other aberrations are perfectly controlled.


For astro I won’t use the lens corrections but light frames to deal with vignetting .. no one cares about straight lines for Milky Way photography so I actually get sharpness and contrast where I need it. Coma is fairly okay, worst case I have to stop it down to f4 .. still better then the EF 16-35mm f4L for Milky Way I reckon, it had more aberrations traded for better corner sharpness.


Big plus for the smooth bokeh and close focusing distance!

most annoying is actually the lack of weather proofing, despite its small size I’d like to leave it out for Astro for a couple of hours and don’t have to take it down during a small drizzle.


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## entoman (Oct 26, 2021)

Andy Westwood said:


> Christopher is also one of my favourite lens reviewers along with Dustin Abbott.


Yes, Christopher Frost is an excellent unbiased reviewer, as are Gordon Laing and Dustin Abbott.

It’s nice to listen to people who can produce a video without jumping up and down shouting “BREAKING NEWS!” like Tony Northrup, and without jabbering at 20 words per second, waving their arms all over the place and talking nonsense like Kai.

Having said that, I do find Jared Polin to be very informative and entertaining, and I have a soft spot for Chris and Jordan on dpreview.


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## dlee13 (Oct 26, 2021)

I’ve had this lens for a week now and I really love it. The only complaint I would make would be the distortion but it’s easily fixed in post and with in body corrections so it’s not a real issue.

The size and weight of this means when I travel it can come everywhere and just be used when something is too wide for the RF 35mm!


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## Frodo (Oct 26, 2021)

mccasi said:


> For astro I won’t use the lens corrections but light frames to deal with vignetting .. no one cares about straight lines for Milky Way photography so I actually get sharpness and contrast where I need it. Coma is fairly okay, worst case I have to stop it down to f4 .. still better then the EF 16-35mm f4L for Milky Way I reckon, it had more aberrations traded for better corner sharpness.


@mccasi , you make an interesting point about not correcting the barrel distortion for astro. Can you post raw or large jpegs of astro photos at f/2.8 and 4 (or links to them)? I'm interested is seeing what corner sharpness is when uncorrected but cropped to about 14mm.
Thanks


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## jam05 (Oct 26, 2021)

victorshikhman said:


> Wasn't the RF mount supposed to allow easier engineering of better designs without these optical weaknesses? Watching this review, the way the focus sounds like the original nifty fifty... It feels like they just slapped this together for lowest possible cost.
> 
> Meanwhile, I'm kicking myself. Two years ago I had a chance to purchase a 24-70 F/4 for $550, and I thought... meh, that's kinda pricey. Now it's going for $1200 on ebay from reputable places. The 16-35 F/4 is also skyrocketing. Maybe supply disruptions are a part of this, but there's still so much demand in good EF lenses, and they're optically no worse than the RF versions. Is Canon leaving money on the table?


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## jam05 (Oct 26, 2021)

You can find them everywhere from $799. $1200 is way too much. Especially for an f4 lens


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## Czardoom (Oct 26, 2021)

Just looking at the image quality comparisons at the-digital-picture.com and the corrected lens results actually look pretty good in the corners (as well as everywhere else). I guess it depends on what you expect - plus I think some anti-auto correct bias happening. In the corners, it's a lot better than the EF 17-40 L lens, for example. And at f/4 only a very slight (negative) difference (at least to my eye) with the EF 16-35 f/4 in the corners. Very slight. The corners are, of course, softer corrected than uncorrected, and this is causing a lot of negativity, in my opinion.


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## vangelismm (Oct 27, 2021)

AJ said:


> There are huge big heavy expensive super-corrected lenses, and then there are small, simple lenses like this 16/2.8. There is a purpose for each. The 16/2.8 will be a perfect travel/backpacking lens. I will be getting one. The pre-corrected barrel distortion doesn't bother me at all. I think it is quite a clever trick actually. If it helps reduce size, weight and cost, then I'm all for it.
> I do hope Canon develops more lenses in this spirit. For example, it'd be nice if they made an R-mount version of the classic 50/1.4 with double-gauss design rather than the big heavy Sigma 50/1.4 versions. All that would be needed is a modern AF motor, improved coatings, and perhaps a tweak to the optical formula. Yes I know we already have a 50/1.8 in R mount but 1.4 would be nice.


And there are small great lens just like EF 40mm 2.8 and EF-s 24mm 2.8.
This one is not good.


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## InchMetric (Oct 27, 2021)

I call these “sales tax lenses”. Because their cost is about the sales tax on the alternative lenses.


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## SnowMiku (Oct 27, 2021)

It seems a bit silly that you can't turn off distortion correction in camera, what if people want to use that distortion for an artistic effect? They should just leave it up to the user if they want to turn the correction on or off.


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## mccasi (Oct 27, 2021)

SnowMiku said:


> It seems a bit silly that you can't turn off distortion correction in camera, what if people want to use that distortion for an artistic effect? They should just leave it up to the user if they want to turn the correction on or off.


I rather always have a corrected viewfinder… like 99.999% of users. Without corrected viewfinder you cannot tell straight lines or leading lines, let alone the extreme vignetting and guessing how much of the image will be cut off when correcting.

in post I always have RAW files without correction to work with for those use cases where distortion doesn’t matter (such as Astro) or your unlikely artistic extreme distortion 3:2 use case…


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## edoorn (Oct 27, 2021)

It's a pretty nice and decent lens. I've actually used it on a professional assignment last week where I had to be a bit mobile; taking the adapted 16-35 III would be too much but it's easy to pop this in the bag. Client's very happy with the shots


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## Del Paso (Oct 27, 2021)

InchMetric said:


> No. They make some very fine and expensive lenses for the nerds who are allergic to corrections, and they make some lenses that perform nicely as an engineered system for people who want to take great pictures with a light and inexpensive lens.
> 
> Then again, those $100,000 Mercedes S-class sedans drive like crap with all the computerized traction control systems turned off. Can't Mercedes design a decent car anymore? I also hear the U.S. Air Force has some planes that won't even fly without computers ensuring stability. Talk about a step backward! Why can't they all be as smart as me and design things right?


Trouble is: these electronic corrections come at a cost, namely decrease of sharpness due to "corner stretching". But I guess this is acceptable for a $300 lens, designed mostly for street and vlogging.
As to the S Class, no!
I've been working for Daimler long enough to know that not a single Mercedes "drives like crap" , electronics switched off. You certainly lose some traction and stability advantages, but the cars remain stable even at high speeds.
i'm speaking out of experience (Stuttgart and Immendingen test tracks, cars, buses and trucks...).
There once was a real issue with the first A class generation, and, more specifically, with another German luxury car which performed miserably with ESP off. But this is another story...


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## GMCPhotographics (Oct 27, 2021)

With a lens like this, we have to remember that our personal use cases aren't the same for everybody. As a semi-retired wedding photographer, this lens is very useful if you are running a 2 camera prime rig. With an 85/1.2 and a 35/1.4, this lens offers a quick change out for a light weight occasional super-wide. It's small, light and very pocketable. Not everyone needs a 16-35/f2.8 when they prefer a 35/1.4 as their main lens.


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## Rivermist (Oct 27, 2021)

neuroanatomist said:


> Well, $300 is a pretty low cost, relatively speaking. I really do think Canon is planning on launching a sub-$800 FF EOS R, and the RP is now $1000. Having an inexpensive FF body with only costly lenses for it is not a recipe for success. But consider – the combination of the RF 16/2.8, RF 24-105 non-L, and RF 100-400 gives a user a very large focal range for a $1350 outlay.


I would also suggest along the same lines that this RF 16mm is a worthy addition to the 24-240mm all-purpose lens. Together they capture a range of focal lengths that, while not extending to 400mm, is probably still in the 95% of desirable pictures. Throw in the 600mm f:11 as a third and you have a range that is light weight, affordable and yet truly amazing.


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## GMCPhotographics (Oct 27, 2021)

SwissFrank said:


> The RF 50/1.2 is literally ten times sharper than the EF 50/1.2. The RF 24-105/4 has the sharpness of the EF MkII but the size of the far smaller EF MkI. And the EF version is far optically worse than the 85DS or 28-70/2 as these lenses don't even exist in EF. That's before you even look at IS, or optic quality for a given size. No Victor, you're quite wrong on this point as you seem to be on everything else.


Yes that's pretty much the only lens. The ef 50mm f1.2 L was the most intrinsically un-sharp L prime Canon have ever made. Great Bokeh, contrast and flare resistance. Amazingly well built...but weak if wide open sharpness was your only metric. Even stopped down it never really came close to even a 24-70L at 50mm's level of sharpness. I always found the ef 50mm f1.2L's AF to be inconsistent and ponderous in low light too.
Most of the ef L primes are still very usable on the higher density sensor RF cameras. One example, the ef 400mm f2.8 LIS mk 1 is as sharp as the current mk3...it's just a LOT heavier. Another is the ef 135mm f2.0 L...still very very sharp.
Zoom wise, most of the ef mk II/III's are still very current and capable too.
Where the RF mount should excel in is with wide lenses, wider than 35mm. On the Rf mount, retro focus design isn't required because of the lack of a mirror box. 
There's a lot of un-used ef lens formulas that were put on hold and reserved / modified for the RF mount. Can was planning this mount for quote a few years ahead of the EOS r1.


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## Foxdude (Oct 27, 2021)

InchMetric said:


> No. They make some very fine and expensive lenses for the nerds who are allergic to corrections, and they make some lenses that perform nicely as an engineered system for people who want to take great pictures with a light and inexpensive lens.
> 
> Then again, those $100,000 Mercedes S-class sedans drive like crap with all the computerized traction control systems turned off. Can't Mercedes design a decent car anymore? I also hear the U.S. Air Force has some planes that won't even fly without computers ensuring stability. Talk about a step backward! Why can't they all be as smart as me and design things right?


Very well said.


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## scyrene (Oct 27, 2021)

A general question as I am clueless - are distortion corrections applied to video? I'd imagine that took a lot more processing power?


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## koenkooi (Oct 27, 2021)

scyrene said:


> A general question as I am clueless - are distortion corrections applied to video? I'd imagine that took a lot more processing power?


Yes and yes. Every new Digic generation has allowed more DLO to be done in video, with Digic X you get everything minus diffraction correction, if I remember correctly.


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## Sigurd2 (Oct 27, 2021)

Since Canon specifically mentioned astrophotography as a use case for this lens, I may have had to high expectations about how well this would do in this arena vs e.g. Rokino 14mm f2.8 .

But considering image quality reports so far, and the challenges with by wire focus in astrophotography, I think I will end up skipping this one.


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## peters (Oct 27, 2021)

victorshikhman said:


> Wasn't the RF mount supposed to allow easier engineering of better designs without these optical weaknesses? Watching this review, the way the focus sounds like the original nifty fifty... It feels like they just slapped this together for lowest possible cost.


Jeah, well, but it IS a lense at the lowest possible cost? Especialy at this quite good quality at this price point and small size?


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## scyrene (Oct 27, 2021)

koenkooi said:


> Yes and yes. Every new Digic generation has allowed more DLO to be done in video, with Digic X you get everything minus diffraction correction, if I remember correctly.


Cool, thanks!


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## Del Paso (Oct 27, 2021)

SwissFrank said:


> This line of reasoning is moronic, given that, as I already explained, correction of distortion results in destination pixel being AT WORST the average of two source pixels (linearly), and this very forum is full of pros ranting that 22MP is indeed enough for professional work. And again, the review shows the corners are far less sharp than that.
> 
> It's a waste of my time to make me write the same explanation over and over. Just read what I wrote the first time and learn from it and stop making me repost and repost.
> 
> As to Mercedes driving like crap, suffice to say I recall an esteemed automotive journalist writing, that Mercedes must tire of delivering a car it thinks measures up, upon which BMW releases a model that not so much moves the goalposts but chucks them over the horizon. My 2000 M5 is still driving like new and handling great and resale value is a high multiple of any contemporary Mercedes.


1: I'd suggest you take a look at TDP...
2: If you think you're THE authority...
3: Fine if you prefer BMW, and believe MB customers to be idiots, I just don't care.
4: No need to be insulting


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## koenkooi (Oct 27, 2021)

scyrene said:


> Cool, thanks!


I've checked the R5 manual at https://cam.start.canon/fa/C003/manual/html/UG-03_Shooting-1_0190.html:


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## juststeve (Oct 27, 2021)

For those doubting focus by wire with the 16/2.8, perhaps autofocus will work. 

With my R5 I can autofocus on many stars with my 20/1.4 Sigma, 35/1.4 Tamron, 70-200/2.8 L IS, and my 31 year old 300/2.8 L. One needs to find a reasonably good star well above the horizon and it is a good idea to turn the lens to manual focusing once accurate auto focus has been achieved. I have accidentally pressed the focus button while astro photography was going on and had to start over again. Also, my M6 ii will autofocus the 22/2 on night skies.


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## gruhl28 (Oct 27, 2021)

SwissFrank said:


> The lack of a mirror allows mirrorless designs to get as close as they want to the film or sensor. In SLR lenses, that is not possible, so where some lens designs would naturally have elements where the mirror is, those designs must be compromised to allow space for the mirror. It's why the EF 35/1.4 was something like ten times the volume of the Leica M 35/1.4 despite not being appreciably better optically.


This point made me wonder whether mirrorless lenses could now be made as small as typical Leica rangefinder lenses, at least if they were manual focus. And how much additional size would be required to add autofocus?

Hmm, come to think of it, I guess the RF 16mm and the RF 50 mm f/1.8 are about as small as Leica lenses. They don't seem to have the same optical quality as the Leicas, though. A line of small primes with size comparable to rangefinder lenses and very good optical quality would be quite attractive. Even if they were manual focus, with focus peaking I might be willing to give up autofocus for small size, and with IBIS you wouldn't need stabilization in the lenses. I doubt Canon will do this, probably wouldn't sell enough without autofocus, but with small elements they could probably add autofocus without making the lenses too much bigger.


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## Jasonmc89 (Oct 27, 2021)

Shame about those corners..


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## Exploreshootshare (Oct 27, 2021)

I got the 16mm F2.8 two weeks ago and I'm going back and forth about whether I should keep or not. I have until tomorrow to decided whether I'll return it or not. 

On the one hand, it is a cheap lense (at least for RF mount) and it is great value for what it is. Some of the pictures I took look actually pretty decent (some even better than "decent") but the vignetting (nightskies/ nightscapes) drives me nuts and the (in my opinion sometime horrible) IQ in the corners. Just doesn't work for landscapes... 

Since I don't think I'll get any good astro out of it and so I'll needing a more capable UWA leise anyway, so why keep it? But every time I attempt to send it back, I wanna keep it so torn about what to do. Maybe I'll just keep it until an 15-35mm or 14-35mm because affordable. 


Or I'll just wait until 2034 when Sigma finally announces their first RF UWA leise


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## AJ (Oct 27, 2021)

Exploreshootshare said:


> Or I'll just wait until 2034 when Sigma finally announces their first RF UWA leise


Yeah no kidding eh
Sigh...


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## Czardoom (Oct 27, 2021)

Del Paso said:


> Trouble is: these electronic corrections come at a cost, namely decrease of sharpness due to "corner stretching". But I guess this is acceptable for a $300 lens, designed mostly for street and vlogging.
> ....


Yes, corner sharpness is less than the uncorrected lens, but...

Better than the EF 17-40mm f/4L lens.
Very close to the 16-35mm f/4L lens.

It seems more like the reality is that trying to get corner sharpness optically is not so easy to do and was rarely done to the extent that it can be done with digital correction without a high cost and much more weight due to much more glass.


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## AJ (Oct 28, 2021)

Review on TDP: https://www.the-digital-picture.com/Reviews/Canon-RF-16mm-F2.8-STM-Lens.aspx

Quote: "Canon now has wide-aperture, consumer-grade 16mm, 35mm, 50mm, and 85mm prime lenses available in the RF mount. This set of prime lenses creates a solid, lightweight, and affordable general-purpose kit."
What seems to be missing is a 24 mm prime. Maybe it'll be next? An RF incarnation of the 24/2.8?


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## LogicExtremist (Oct 28, 2021)

Czardoom said:


> Yes, corner sharpness is less than the uncorrected lens, but...
> 
> Better than the EF 17-40mm f/4L lens.
> Very close to the 16-35mm f/4L lens.
> ...


Hmmm, not really, there's no comparison between a budget lens and the EF 16-35mm f/4 L lens, which gets reviews like this:

_"If you are looking for an extremely sharp ultra-wide angle zoom lens, the Canon EF 16-35mm f/4L IS USM Lens should be at the top of your consideration list. This lens delivers prime-grade image sharpness right into full frame corners and it has the overall performance to match, including AF speed and accuracy." _(https://www.the-digital-picture.com/Reviews/Canon-EF-16-35mm-f-4-L-IS-USM-Lens.aspx)

There is no substitute for optical correction when it comes to corner sharpness on a wide lens, because the corrections must add in pixels that aren't really there. Of course, people will start arguing about accuracy of the software algorithms that guess what the pixels should be, but that's a moot point. Some post processing operations add data that was never there and also result in a loss of sharpness. Objectively, we can simply look at the images produced after software correction and clearly see that the corners are soft, end of story. 

There is a bit of a strange rationalisation process going on with some comments. Not a criticism of any particular person here, I wish people can just let this little budget lens be what it is, and appreciate it for what it can do, rather than fuss over what it isn't and cant do. Denying or playing down its limitations isn't really helpful either in my opinion.

We basically have a compact, lightweight and cheap 16mm lens with a fast aperture, which is sharp in the centre and soft in the corners. That means it's not good for serious landscape photography, can't be used for astro unless stopped down to f/4, but makes an awesome carry around lens where a wide angle is needed but the corners don't matter. Casual landscape and group photos, vlogging and talking head videos come to mind. Any other applications?

One thing that baffles me is the questionable logic justifying software corrections on more expensive lenses. Like all engineering compromises, they come at a cost, and they can be made in Canon's favour, NOT the buyers! They can skimp on the lens formula, use software corrections to compensate, and sell the lens for the same price as an optically corrected one, but make a bigger profit. That's one possibility. Is that's what's happening? You guys tell me, are software corrected RF lenses selling at a cheaper price than optically corrected equivalents if such exist? Or is it not an apples for apples comparison because they're just trading a bit more sharpness for a lot more distortion?

Each lens has a specific use case, and where such compromises are fine, then so be it, if not, then it's necessary to use a lens with decent enough optics to captures all the data required for the necessary image quality. otherwise it's a pointless game of justification and self deception like this video!


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## HMC11 (Oct 28, 2021)

LogicExtremist said:


> Hmmm, not really, there's no comparison between a budget lens and the EF 16-35mm f/4 L lens, which gets reviews like this:
> 
> _"If you are looking for an extremely sharp ultra-wide angle zoom lens, the Canon EF 16-35mm f/4L IS USM Lens should be at the top of your consideration list. This lens delivers prime-grade image sharpness right into full frame corners and it has the overall performance to match, including AF speed and accuracy." _(https://www.the-digital-picture.com/Reviews/Canon-EF-16-35mm-f-4-L-IS-USM-Lens.aspx)
> 
> ...


Thank you for a clear-minded take. Dustin Abbott just released his review of the RF 14-35 f4. It seems that the lens follows a similar approach as the RF 16mm in that it relies on software to do some fairly major corrections, and that actual image is wider than 14mm but crops in to remove the 'physical' vignetting. Despite this, it seems that the 14-35 is still very sharp at almost the entire range (except at 35mm) when wide-open, which makes it a viable landscape lens. While psychologically it doesn't feel good to know at the back of the mind that the image is fairly heavily software corrected, the end results may well be more than satisfactory. Overall, had it been priced closer to the EF16-35, the 14-35 could be a fairly compelling purchase for me. Given the significant price difference, I am somewhat hesitant. I may just have to bite the bullet and get it if this is going to be the 'standard' approach in order to get a lighter and smaller lens with very good final image output.


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## LogicExtremist (Oct 28, 2021)

HMC11 said:


> Thank you for a clear-minded take. Dustin Abbott just released his review of the RF 14-35 f4. It seems that the lens follows a similar approach as the RF 16mm in that it relies on software to do some fairly major corrections, and that actual image is wider than 14mm but crops in to remove the 'physical' vignetting. Despite this, it seems that the 14-35 is still very sharp at almost the entire range (except at 35mm) when wide-open, which makes it a viable landscape lens. While psychologically it doesn't feel good to know at the back of the mind that the image is fairly heavily software corrected, the end results may well be more than satisfactory. Overall, had it been priced closer to the EF16-35, the 14-35 could be a fairly compelling purchase for me. Given the significant price difference, I am somewhat hesitant. I may just have to bite the bullet and get it if this is going to be the 'standard' approach in order to get a lighter and smaller lens with very good final image output.


Good point, it depends on which way Canon is planning to go with their RF lenses in terms of design strategy. The new mirrorless platform provides a convenient cover for the use of software correction, which can be used as a way of giving less and charging more for it.

I looked at thedigitalpicture.com review, where the author of the article points out the issue of AI generated fake detail in the corners, but then plays that down:

_"Stretching the image out to the as-framed composition requires AI. Although today's image correction AI is very good, AI does not really know what the subject details were in the stretched areas, and calling the result fake detail does not seem untrue.

Does the strong distortion correction matter? Psychologically it does, and an image captured from a non-distorted lens can similarly be up-sized to even higher resolution using AI, potentially giving it an advantage. That said, did you notice any corner issues until this point in the review? Likely not substantial ones.

I need to get over the psychological issue of the geometric distortion correction, but otherwise, this lens is a stellar performer."_

I'm not sure how he can reduce the issue of AI generated fake detail in the corners down to a psychological issue, when it's actually an image reproduction issue that is visible. Surely, some subjects won't be affected, and what's good enough might be subjective, but here we're talking about a crop of the full image and a smearing of details on an L-series pro-grade lens that is not cheap. I can accept that as a compromise on the handy little RF 16mm f/2.8 budget lens, but that's an entry level budget lens! 

The Rf 14-35mm Ff/4 L should be usable for landscape like the EF 16-35 f/4 L, and no amount of arguments can justify missing corner details because the optics can't deliver them. What the review ignores is that images most likely will be post-processed, and with a combination of heavy vignetting and AI generated fake detail, the details might degrade further and start to fall apart with certain post-processing tasks.

The correction also crops the image, so for those who fuss over details and maximum pixels over the subject, the whole sensor is not used, and this might not be much of a pixel loss percentage-wise, but it's nevertheless there.

So what do we get for the more expensive Rf lens compared to its EF counterpart? Doesn't look like much in terms of image quality, even when the corner issue is ignored.

_"In the image quality comparison, the two lenses show rather similar image quality overall. Both lenses have slight advantages in specific comparisons. For example, the RF lens produces sharper periphery image quality at 28mm, and the EF lens is sharper in the center of the frame at 35mm f/4. Performing similarly in this comparison reflects positively on the RF lens — this EF lens is a great performer. The RF lens has dramatically stronger geometric distortion and has stronger lateral CA. The EF lens shows stronger peripheral shading at 35mm f/4 and slightly less at narrower apertures in the wider half of the focal length range."_

Lens image comparison tool for Rf 14-35 f/4 L and EF 16-34 f/4 L here.

(https://www.the-digital-picture.com/Reviews/Canon-RF-14-35mm-F4-L-IS-USM-Lens.aspx)

I'm kind of glad I got the EF 16-35mm f/4 almost new a while back, I can't see much benefit for me in upgrading. For others, if having the native RF mount, 175g less weight and 2mm extra at the wide end is important, then there isn't much choice, other than paying not that much more, relatively speaking, and stepping up to the 15-35mm f/2.8 which is a much better engineered lens.

We may be stepping into a whole new era of different compromises with the new RF range. We know they all have a heavy vignetting problem that's due to the RF mount design, and I can live with that. We've seen a molded plastic lens element included in the Rf 100-400, and some radical geometric distortion in a few lenses being rectified with software correction. Compromises imply that you give something to gain something else, and if we're not gaining much over the older EF lenses, but paying more, then we need to ask whether these are just cost cutting measures, or if we're gaining enough to offset what is being lost. Obviously, this will vary from lens to lens, and each needs to be considered against the buyers requirements.


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## neuroanatomist (Oct 28, 2021)

HMC11 said:


> I may just have to bite the bullet and get it if this is going to be the 'standard' approach in order to get a lighter and smaller lens with very good final image output.


I think it is going to be the standard approach. Sony and Fuji have been doing this for years, even in high end lenses. Think about how many people on this forum have clamored for Canon to ‘keep up with the competition’. I guess they are.


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## LogicExtremist (Oct 28, 2021)

neuroanatomist said:


> I think it is going to be the standard approach. Sony and Fuji have been doing this for years, even in high end lenses. Think about how many people on this forum have clamored for Canon to ‘keep up with the competition’. I guess they are.


Reminds me of the old saying "be careful what you wish for!"


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## Tom W (Oct 28, 2021)

Canon Rumors Guy said:


> Continue reading...


Interesting lens, and a good price, but I'm a little concerned at the excessive  use of software corrections to make up for large lens weaknesses. I suppose it's a tradeoff for getting an ultra-wide that is this small and inexpensive, but I'd prefer less correction and better lens capability. I suppose that for $300, what I'm asking for is not necessarily possible.


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## gruhl28 (Oct 28, 2021)

I'm not sure this talk of "adding pixels" and using AI and creating things that weren't there is accurate. Does distortion correction really need or even use AI? Distortion correction has been around for years in LR, Photoshop, etc., long before anyone was talking about AI in post-processing. Distortion correction crops out some pixels and moves others, and maybe it averages and interpolates some to create new ones, I'm not sure. But it doesn't add things to the side of the frame, it actually crops out the sides, and it doesn't require AI to average two adjacent pixels to create a new one. Sure, this can magnify other aberrations and soften the image, but it's the final image that counts. If the corners are sharp even after distortion correction, as they are with the 14-35, then what difference does it make? The lens must be really sharp in the corners in order for the final pic to still be sharp after the stretching. Even with the corners of the 16mm not being as sharp as we would like, would even this level of quality have been possible in a lens this size and price without using distortion correction?

The statement made earlier, "The Rf 14-35mm Ff/4 L should be usable for landscape like the EF 16-35 f/4 L, and no amount of arguments can justify missing corner details because the optics can't deliver them" is wrong in my opinion. The RF 14-35 is not missing corner details - the corner detail is extremely good, just look at the pictures. This detail wasn't just "made up", it is because the lens is so sharp that even after stretching the result is still excellent. The designers sacrificed some optical distortion correction for excellent sharpness and other benefits, knowing that the distortion could be easily corrected in software, whereas a lack of resolution cannot be corrected - to make up for lack of resolution really would require AI. If AI were "creating" this detail then the16mm would have "sharp" corners also.


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## LSXPhotog (Oct 28, 2021)

It's a shame that Canon has taken so long to release lens profiles for new RF glass to Adobe because the cat's out of the bag on this lens now...it's a lens that requires a truly hilariously amount of correction to create a presentable image. I'm finding it to be a brilliant lens for video and I purchased it exclusively as a gimbal ultra-wide for real estate video - which I'm confident it will do very well in. However...this lens is not a very good photography lens in regards to corner performance even after correction. It may be better to just crop the image even further to an 18-20mm to actually get good results. Things deteriorate rapidly at the corners of the frame - not a problem for video. It's just very sad that I was hoping for a better performance in the corners. I'll take it out a bunch next week and see if my opinion on it changed in regards to photography.


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## HenryL (Oct 28, 2021)

LSXPhotog said:


> It's a shame that _*Adobe*_ has taken so long to _*develop*_ lens profiles for new RF glass...


FTFY...


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## HMC11 (Oct 28, 2021)

LogicExtremist said:


> Good point, it depends on which way Canon is planning to go with their RF lenses in terms of design strategy. The new mirrorless platform provides a convenient cover for the use of software correction, which can be used as a way of giving less and charging more for it.
> 
> I looked at thedigitalpicture.com review, where the author of the article points out the issue of AI generated fake detail in the corners, but then plays that down:
> 
> ...


As I don’t have the EF 16-35, I may need to do some mental gymnastics to persuade myself that this is worth going for . From ‘The digital picture’ review you shared, the distortion at 16mm seems not too bad. If so, I could take this as a RF 16-35 f4 lens, and that the premium over the EF version is for it being lighter, smaller, a tad sharper, better IS, and the control ring. Besides, with the EF launch price at $1199 in 2014 being about $1390 today, the ‘actual’ premium would be about $300. That may be easier to swallow .


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## neuroanatomist (Oct 28, 2021)

LogicExtremist said:


> The correction also crops the image, so for those who fuss over details and maximum pixels over the subject, the whole sensor is not used, and this might not be much of a pixel loss percentage-wise, but it's nevertheless there.


The issue there is that means it’s not just fake details in the corners after geometric corrections. The R3 outputs a 6000x4000 pixel RAW file. I presume that even though the wider-than-14mm image is cropped to a 14mm FoV without mechanical vignetting, the output will remain 6000x4000. That suggests that the cropped image must be up-scaled…fake pixels across the whole image.

I don’t know if that’s true, will be interesting to see if the RAW images at 14mm have larger pixel dimensions (i.e., use some of the non-effective pixels). 



LogicExtremist said:


> I'm kind of glad I got the EF 16-35mm f/4 almost new a while back, I can't see much benefit for me in upgrading. For others, if having the native RF mount, 175g less weight and 2mm extra at the wide end is important, then there isn't much more choice, other than paying not that much more relatively speaking and stepping up to the 15-35mm f/2.8 which is a much better engineered lens.


The RF is significantly shorter and lighter, for me that’s useful for travel. Although I sometimes travel with the 11-24/4 and the 17+24 TS-E, But sometimes I want a smaller and lighter kit and the 14-35 and 24-105 will make a nice kit for those occasions.


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## neuroanatomist (Oct 28, 2021)

SwissFrank said:


> You have to stop it with the goddamn AI fake detail BS. Go sit in a corner and breath deeply until you can talk rationally.


Take a chill pill, or better yet some real medication. AI is a hip term that people toss around indiscriminately, when what they really mean is simply the use of algorithms.

My Mac runs those algorithms on a ‘neural engine’…is that AI? I don’t think anyone really cares, except apparently you.


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## HMC11 (Oct 28, 2021)

gruhl28 said:


> The statement made earlier, "The Rf 14-35mm Ff/4 L should be usable for landscape like the EF 16-35 f/4 L, and no amount of arguments can justify missing corner details because the optics can't deliver them" is totally wrong. The RF 14-35 is not missing corner details - the corner detail is extremely good, just look at the pictures. This detail wasn't just "made up", it is because the lens is so sharp that even after stretching the result is still excellent. The designers sacrificed some optical distortion correction for excellent sharpness and other benefits, knowing that the distortion could be easily corrected in software, whereas a lack of resolution cannot be corrected - to make up for lack of resolution really would require AI. If AI were "creating" this detail then the16mm would have "sharp" corners also.


Kindly correct me if I got this wrong. My understanding of the statement is that the optics projects an image that is a little wider than 14mm, and the software crops that to give a 14mm field of view as part of the correction process. If so, there would be some loss of pixels compared with a lens that projects an image with a 14mm FoV that covers the entire sensor. Thus, the statement is not incorrect as the optical design 'can't deliver' a 14mm FoV that covers the whole sensor but has to resort to a wider FoV and cropping to correct the distortion. Having said this, I do agree that if the image corners are sharp, and that to all intent and purposes one can't tell whether there are 'fake' pixels added, then it would make little material difference to someone looking at the image in the size, viewing distance etc that it is intended for.


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## LogicExtremist (Oct 29, 2021)

HMC11 said:


> Kindly correct me if I got this wrong. My understanding of the statement is that the optics projects an image that is a little wider than 14mm, and the software crops that to give a 14mm field of view as part of the correction process. If so, there would be some loss of pixels compared with a lens that projects an image with a 14mm FoV that covers the entire sensor. Thus, the statement is not incorrect as the optical design 'can't deliver' a 14mm FoV that covers the whole sensor but has to resort to a wider FoV and cropping to correct the distortion. Having said this, I do agree that if the image corners are sharp, and that to all intent and purposes one can't tell whether there are 'fake' pixels added, then it would make little material difference to someone looking at the image in the size, viewing distance etc that it is intended for.


If you're saying that the lens projects a distorted image wider than 14mm across the whole sensor, then crops to a smaller size to create a 14mm FOV, then yes, that's what I believe is happening. 

It looks like some people don't quite get that an image only contains the data that was captured when the photo was taken. If corners are really heavily vignetted, then the amount of detail recoverable from the shadows will be whatever the camera is capable of recovering if you underexposed by so many stops. If geometric distortion of a lens is so bad that extra pixels need to be generated to flatten an image, then we're looking at computational photography, much like what happens on a smartphone.

Is there a price to pay for adding computer generated pixels to create fake data for filling in corner details that were never actually captured in the first place? Well, of course, as the computer has no idea what the corners were meant to look like, and just uses a fancy mathematical formula, a computer algorithm, to guess what the pixels might be.

Seeing is believing, so I've created a very clear comparison to show this effect, by comparing the *Canon RF 16mm F2.8 STM Lens vs Canon RF 50mm F1.8 STM Lens*. Similar sized lenses, with comparable price and build quality, the difference being software correction.

*Check out the comparison tool below, what happens when we stop down the lenses to f/8:*









Canon RF 16mm F2.8 STM Lens Image Quality


View the image quality delivered by the Canon RF 16mm F2.8 STM Lens using ISO 12233 Resolution Chart lab test results. Compare the image quality of this lens with other lenses.




www.the-digital-picture.com





The RF 50mm gets sharper as we stop down, and by f/8 is VERY sharp in the corners. When we look at the RF 16mm, we see that stopping down has no effect on sharpness in the corners, because the corner data was never actually captured optically in the first place, and as a consequence, doesn't sharpen with a narrower aperture. The corners stay blurry right through the aperture range because they're being digitally filled. Feel free to set both lenses in the tool to f/2.8 then compare from there through the aperture range. Hope this helps people understand what's going on here, the goal is understanding to make better and more informed buying decisions, it's not a competition or an attack on anyone's values!


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## LogicExtremist (Oct 29, 2021)

For the people that had questions about the software correction on the RF 14-35mm, Dustin Abbot has some great information - https://dustinabbott.net/tag/14-35mm/

See cut & paste below, which explains that the lens optics are actually wider than 14mm, but mechanical vignetting is so high that all data is lost under the pure black corners, so it has to be cropped away. After cropping the image is only equivalent to a 15mm FOV. If the sensor is capturing all the uncorrected data (20MP on an R6), but the final images are still the full sensor size of megapixels (20MP) after the in-camera cropping, then it probably means the image is being digitally enlarged too, because the extra pixels didn't appear from thin air.

This is what Dustin Abbot has to say in his review:_

"Note those corners? That is actually mechanical vignetting, or a place where the lens actually doesn’t quite cover the full frame image circle. What you are are seeing is part of a lens’ circular opening iris that didn’t quite cover the rectangular sensor, so only the corners show dark. This isn’t lens vignetting in the traditional sense, as something physical is actually blocking light from reaching that portion of the sensor. Unlike typical vignette, this mechanical vignette will be there regardless of what aperture you choose; it is just as strong at F8 as it is at F4. I’ve seen this with superzoom or cheaper lenses, but I can’t recall seeing this on a professional grade zoom.


So let’s dive in a see what’s going on. Below is a sequence of three images, though this is actually all the same image. The first is the RAW file as it arrived in Lightroom (though with a white balance correction; the R5 is [for some reason] really terrible with the auto white balance on my test chart), the second is my attempt at manually correction the image, and the final is the JPEG image as it was corrected in camera.













Of the three, the JPEG is clearly the cleanest, though if you compare it to the previous images, you will see just how much of the frame is lost to achieve that final correction. What you see in the JPEG was how I framed the chart in camera, but the resulting RAW file was very loose in the frame because of how much space Canon is leaving for correction of both the heavy distortion and the various vignette issues. The distortion is extremely heavy; it required a +34 to achieve this manual correction, and it is also is not linear, so that results in a “mustache” pattern left behind. The standard correction profile obviously does a much cleaner job on the JPEG, and will on RAW images as well when that profile arrives.


I said “various vignette issues” as there are actually two separate issues here. The mechanical vignette issue can only be solved via cropping, as there is no picture information under that pure black in the corners. The traditional distortion is also very heavy, however, requiring me to max out the vignette slider at +100 and sliding the midpoint to zero. We are talking at least 3 stops of vignette, perhaps a bit more.


The heavy need for corrections also plays a bit of havoc with the focal length. On paper, the 14-35L is actually bit wider than the Samyang AF 14mm F2.8 prime lens which I used for comparison as it is the only other RF mount 14mm lens I had on hand. I put both lenses on a tripod and shot a brick wall scene to test width. Sure enough, the uncorrected image from the RF 14-35L is wider, though with some major problems, as you can see.






But I grabbed the corrected JPEGs from both lenses, and found, unsurprisingly, that now the Samyang’s image was actually wider. There are blocks showing on Samyang image (right) that are completely clipped off on the Canon’s image. I would say the corrected image from the Canon probably behaves more like a 15mm lens. "_

To quote a poster on dpreview, "You should know the outsides of the image are going to be soft due to the amount of distortion correction. No amount of stopping down can fix squeezing 2 pixels worth of image into one pixel on the camera sensor." That, in a nutshell is the truth. If your photography is unaffected by this, then these lenses are an option for you, if not, then they're not the right tool for the job.


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## LogicExtremist (Oct 29, 2021)

HMC11 said:


> As I don’t have the EF 16-35, I may need to do some mental gymnastics to persuade myself that this is worth going for . From ‘The digital picture’ review you shared, the distortion at 16mm seems not too bad. If so, I could take this as a RF 16-35 f4 lens, and that the premium over the EF version is for it being lighter, smaller, a tad sharper, better IS, and the control ring. Besides, with the EF launch price at $1199 in 2014 being about $1390 today, the ‘actual’ premium would be about $300. That may be easier to swallow .


If I didn't have the EF lens, and I wanted the get a wide angle f/4 zoom, the 14-35mm is the only one available for the RF mount and I would consider it rather than invest in an old mount lens. The two considerations are value for money and image quality. If the IQ is suitable for your requirements, then it might be a matter of waiting till the Xmas or EOFY sales arrive!


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## BBarn (Oct 29, 2021)

Both the RF 16 and RF 14-35 have substantial uncorrected geometric distortion. After correction, corner sharpness of the RF 14-35 is very good, while the RF 16's is only fair. This tells me that distortion correction alone does not substantially reduce sharpness.


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## LogicExtremist (Oct 29, 2021)

BBarn said:


> Both the RF 16 and RF 14-35 have substantial uncorrected geometric distortion. After correction, corner sharpness of the RF 14-35 is very good, while the RF 16's is only fair. This tells me that distortion correction alone does not substantially reduce sharpness.


Well, you can't draw that conclusion because its not an equal comparison. The better optics in the L-series lens would actually resolve a higher level of detail. There are reports that the images from software corrected lenses look worse on lower megapixel cameras, such as the R6 compared to the R5, because a higher megapixel sensor will capture much more data for the same part of an image, When you start with more accurate data, or more data, a fixed amount of image degradation due to software correction wont mess us the photo as badly, that's all we're seeing here.

The simple way to objectively test how much the software correction affects the image quality of the lens is to *compare the RF 14-35mm f/4 lens to itself*, by checking what happens to the periphery and corners when the lens is stopped down. Typically, lenses get sharper edge to edge when stopped down to a narrower aperture. Try the lens comparison below, which compares the sharpness of the lens at f/4 to the sharpness at f/8:









Canon RF 14-35mm F4 L IS USM Lens Image Quality


View the image quality delivered by the Canon RF 14-35mm F4 L IS USM Lens using ISO 12233 Resolution Chart lab test results. Compare the image quality of this lens with other lenses.




www.the-digital-picture.com





What is curious is that stopping down just reduces the vignetting, brightening up the image a bit, but does not improve sharpness at all! 

Why? Like I said earlier, you can't stop down to sharpen pixels that were never captured in the first place but were added in after the fact.


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## BBarn (Oct 29, 2021)

LogicExtremist said:


> Well, you can't draw that conclusion because its not an equal comparison. The better optics in the L-series lens would actually resolve a higher level of detail.


The RF 14-35 is sharper in the corners after correction because it was sharper in the corners before correction. The RF 16 isn't as sharp in the corners after correction because it wasn't as sharp in the corners before correction. It's that simple. Distortion correction does not have a major effect on corner sharpness.


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## LogicExtremist (Oct 29, 2021)

BBarn said:


> The RF 14-35 is sharper in the corners after correction because it was sharper in the corners before correction. The RF 16 isn't as sharp in the corners after correction because it wasn't as sharp in the corners before correction. It's that simple. Distortion correction does not have a major effect on corner sharpness.


Totally agree 100% with you on the first statement. Distortion correction doesn't have a major effect on corner sharpness? Those two lens test tools I posted for each of these lenses would suggest otherwise _in my eyes_, but if the image degradation doesn't look that bad to you, I can't argue with that...

For me, that level of software correction might be okay on the budget lenses when used for specific purposes such as the the 16mm f/2.8 STM used a a vlogging/video lens and the RF 24-240mm F4-6.3 IS USM as a lightweight do-everything travel lens, but not on a high-end L-series lens at that price. 

As they say, YMMV (your mileage may vary), the satisfaction level might be different for every person.


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## LogicExtremist (Oct 29, 2021)

Okay folks, found a decent review of this lens here - 




Incidentally, one of the viewer comments on this video describes some testing they did with the RF 16mm f/2.8 STM and it's very telling, see below:

_"In Lightroom, I used the EF 16-35 F2.8 L II's profile and manually slide the distortion to 3/4, then in the manual correction tab, distortion correction is set to 100. After cropping to closely match the composition of the same photo's in-camera processed JPG,* I found out the crop results in a 29% loss of the sensor's real estate (21.42 mp vs 30.11 mp on the EOS R)*, which means the true resolution of the sensor is also lost. If you shoot full-sized jpgs in camera, it means 29% of the pixels are results of computation. It's hilarious when you think of it. Canon's definitely cheating in these newer lightweight ultra wide-angle lenses (the 14-35 F4 included) to digital corrections and fake resolutions. Video was fine as there's in camera correction. However, you are still giving up a lot of pixels for the same reason. I also think the lens will be unusable on other cameras that use RF mounts, like the RED v-raptor, as there will be no correction data applied to the footage. It's essentially an uncorrected 13mm or 14mm lens, faked into a 16mm by warping and cropping the image. I do not agree with this approach at all. I would rather see a proper but much bigger and more expensive design"_

This is what I was suspecting...

The reviewer described it as a decent video lens, and suggested that it would make an excellent 24mm equivalent RF mount APSC lens, if Canon ever does release a crop sensor body, because it would only use the sharper centre portion of the lens.

Not sure why some people are a bit reluctant to dig a bit deeper to get a better understanding of what's going on.


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## koenkooi (Oct 29, 2021)

LogicExtremist said:


> Okay folks, found a decent review of this lens here -
> 
> 
> 
> ...


So essentially: "I wish this cheap, light non-L lens was an expensive, heavy L lens." It's not like you can see from the outside how small and light it is.....


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## LogicExtremist (Oct 30, 2021)

koenkooi said:


> So essentially: "I wish this cheap, light non-L lens was an expensive, heavy L lens." It's not like you can see from the outside how small and light it is.....


That's not what the reviewer is saying! Did you even watch the review? He points out its pros and cons, and the small, compact pocketable size is virtually one of the things he mentions. He works as a photographer and he's pointing out the flaws which make it unsuitable for many of the traditional applications of a 16mm prime!


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## gruhl28 (Oct 30, 2021)

LogicExtremist said:


> Well, you can't draw that conclusion because its not an equal comparison. The better optics in the L-series lens would actually resolve a higher level of detail. There are reports that the images from software corrected lenses look worse on lower megapixel cameras, such as the R6 compared to the R5, because a higher megapixel sensor will capture much more data for the same part of an image, When you start with more accurate data, or more data, a fixed amount of image degradation due to software correction wont mess us the photo as badly, that's all we're seeing here.
> 
> The simple way to objectively test how much the software correction affects the image quality of the lens is to *compare the RF 14-35mm f/4 lens to itself*, by checking what happens to the periphery and corners when the lens is stopped down. Typically, lenses get sharper edge to edge when stopped down to a narrower aperture. Try the lens comparison below, which compares the sharpness of the lens at f/4 to the sharpness at f/8:
> 
> ...


I agree that the way to objectively test how much the software correction affects the image quality of the lens is to compare the RF 14-35 to itself, or the 16mm to itself, but not by stopping down - by comparing the sharpness of the lens uncorrected with the sharpness after corrections. It's as simple as that; how does what ends up in the corners look before corrections vs. after corrections.


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## gruhl28 (Oct 30, 2021)

BBarn said:


> The RF 14-35 is sharper in the corners after correction because it was sharper in the corners before correction. The RF 16 isn't as sharp in the corners after correction because it wasn't as sharp in the corners before correction. It's that simple. Distortion correction does not have a major effect on corner sharpness.


I totally agree with the first part. As for how much distortion correction affects corner sharpness, the test is to simply compare the sharpness before vs. after correction. I'm not sure how much it affects sharpness, as I don't have 100% crops before and after correction, but someone who has the lenses can easily make this comparison.


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## LogicExtremist (Oct 30, 2021)

gruhl28 said:


> I agree that the way to objectively test how much the software correction affects the image quality of the lens is to compare the RF 14-35 to itself, or the 16mm to itself, but not by stopping down - by comparing the sharpness of the lens uncorrected with the sharpness after corrections. It's as simple as that; how does what ends up in the corners look before corrections vs. after corrections.


Apologies, I don't quite understand because the original corners are cropped off the uncorrected image and therefore change position on the corrected image.


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## gruhl28 (Oct 30, 2021)

LogicExtremist said:


> Totally agree 100% with you on the first statement. Distortion correction doesn't have a major effect on corner sharpness? Those two lens test tools I posted for each of these lenses would suggest otherwise _in my eyes_, but if the image degradation doesn't look that bad to you, I can't argue with that...
> 
> For me, that level of software correction might be okay on the budget lenses when used for specific purposes such as the the 16mm f/2.8 STM used a a vlogging/video lens and the RF 24-240mm F4-6.3 IS USM as a lightweight do-everything travel lens, but not on a high-end L-series lens at that price.
> 
> As they say, YMMV (your mileage may vary), the satisfaction level might be different for every person.


Not all aberrations are corrected by stopping down. You cannot assume that because corners are not improving when stopping down that that means that you are seeing constructed pixels that were never captured in the first place. I dont' know why so many people are missing the obvious - to see how much distortion correction affects sharpness, or resolution, or whatever, simply compare those in the uncorrected image with the corrected image.


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## gruhl28 (Oct 30, 2021)

LogicExtremist said:


> Apologies, I don't quite understand because the original corners are cropped off the uncorrected image and therefore change position on the corrected image.


Look at the details that are in the corners after correction. Then look at that same part of the image before correction, the same details, which won't be all the way in the corners in this image. How do the sharpness, resolution, contrast compare?


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## gruhl28 (Oct 30, 2021)

LogicExtremist said:


> Okay folks, found a decent review of this lens here -
> 
> 
> 
> ...


If those numbers are accurate, and it is actually cropping out 29% of the image, that is a significant loss of resolution. That statement was not in the video, though, it was in a comment from someone else, so we don’t know if it is accurate or not.


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## LogicExtremist (Oct 30, 2021)

gruhl28 said:


> Look at the details that are in the corners after correction. Then look at that same part of the image before correction, the same details, which won't be all the way in the corners in this image. How do the sharpness, resolution, contrast compare?


You'd probably need to crop the uncorrected to match the size of the corrected image in that case to make the comparison a bit easier visually, yeah that makes sense!


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## LogicExtremist (Oct 30, 2021)

gruhl28 said:


> If those numbers are accurate, and it is actually cropping out 29% of the image, that is a significant loss of resolution.


That would definitely be a cause for concern, even more so for photos than video. It would be interesting to see how much those software-corrected images would hold up to extensive post processing like what is usually done with landscape photos, to see how the details hold up or whether the images begin to fall apart and start producing artifacts more readily.


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## Random Orbits (Oct 30, 2021)

LogicExtremist said:


> That would definitely be a cause for concern, even more so for photos than video. It would be interesting to see how much those software-corrected images would hold up to extensive post processing like what is usually done with landscape photos, to see how the details hold up or whether the images begin to fall apart and start producing artifacts more readily.


It depends on what you're comparing this to. It's a $300 lens. Yes, something like the RF 15-35 f/2.8L IS would be better, but that is over 2k. For absolute IQ, I'd choose the L lens, but this might come in handy if weight is a primary factor or for snapshots where the subject is in the center. If I'm trying to save weight, I might opt for the ultrawide zoom, the nifty fifty and a telephoto. Some my opt for this RF 16, a standard zoom and a telephoto. I do like that it's the same size as the RF 50 f/1.8.


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## BBarn (Oct 30, 2021)

If geometric distortion correction caused a substantial reduction in sharpness, the corners of the RF 14-35 (which requires substantial geometric correction) wouldn't be sharp. But they are. Easy peasy. Geometric distortion correction can be accomplished with relatively little negative impact to image sharpness. If you want to know why the RF 16 isn't sharp in the corners, look elsewhere.


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## gruhl28 (Oct 30, 2021)

LogicExtremist said:


> That would definitely be a cause for concern, even more so for photos than video. It would be interesting to see how much those software-corrected images would hold up to extensive post processing like what is usually done with landscape photos, to see how the details hold up or whether the images begin to fall apart and start producing artifacts more readily.


It would also be interesting to know whether jpg's and Raws processed in DPP lose 29% of their pixels, or whether Canon is actually doing something to "construct" additional pixels, whether that is simple interpolation or AI.


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## BBarn (Oct 31, 2021)

EXIF data shows the corrected image sizes of both RAW and JPG (large) files taken with the RF 16mm f/2.8 match the full sensor pixel count.


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## Aussie shooter (Oct 31, 2021)

juststeve said:


> For those doubting focus by wire with the 16/2.8, perhaps autofocus will work.
> 
> With my R5 I can autofocus on many stars with my 20/1.4 Sigma, 35/1.4 Tamron, 70-200/2.8 L IS, and my 31 year old 300/2.8 L. One needs to find a reasonably good star well above the horizon and it is a good idea to turn the lens to manual focusing once accurate auto focus has been achieved. I have accidentally pressed the focus button while astro photography was going on and had to start over again. Also, my M6 ii will autofocus the 22/2 on night skies.


I have the R6(which auto focuses at the same level as the R5) and absolutely get better focus by manually focusing while zoomed in ten times.


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## neuroanatomist (Oct 31, 2021)

LogicExtremist said:


> If I didn't have the EF lens, and I wanted the get a wide angle f/4 zoom, the 14-35mm is the only one available for the RF mount and I would consider it rather than invest in an old mount lens. The two considerations are value for money and image quality. If the IQ is suitable for your requirements, then it might be a matter of waiting till the Xmas or EOFY sales arrive!


I just sold my EF 16-35/4L IS.

The degree of cropping are reported for the 16/2.8 seems excessive, and given that it was an unsubstantiated comment on a review I take it with a large grain of salt. Regardless, to deliver the camera’s full resolution, the cropped images must be upscaled.

I also don’t find a comparison between two corrected profiles (Canon 14-35 vs Samyang 14) to be especially compelling. Distortion correction changes framing, and the degree to which distortion is corrected may differ between the profiles.

I am pretty sure that if Canon labels a lens 16mm or 14mm, the FoV delivered in the final images will be that. Keep in mind that focal length is specified at infinity focus. Since people testing for lens distortion aren’t using charts or walls large enough to fill the frame with the lenses focused at infinity, focus breathing must be considered. For example, the EF-S 18-200mm at the long end frames at ~150mm equivalent with a close subject, the EF 100/2.8L Macro frames like ~67mm at 1:1. The 16/2.8 probably has a fair bit of breathing, the 14-35 less so. 

For me, an additional factor is the small size of the 14-35, compared to the 16-35/4 (with adapter). Also, the relevant comparison to me is both lenses at the wide end, so even if the 14-35 isn’t quite 14mm, it’s wider than 16mm, and smaller and lighter in my bag. 

I ordered the RF 14-35, once it arrives I’ll run some comparisons, including vs my EF 11-24 for FoV.


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## LogicExtremist (Oct 31, 2021)

neuroanatomist said:


> I just sold my EF 16-35/4L IS.
> 
> The degree of cropping are reported for the 16/2.8 seems excessive, and given that it was an unsubstantiated comment on a review I take it with a large grain of salt. Regardless, to deliver the camera’s full resolution, the cropped images must be upscaled.
> 
> ...


When you test your RF 14-35mm f/4, can you please compare the uncorrected and software corrected images to confirm the extent of cropping that occurs? Thanks


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## neuroanatomist (Oct 31, 2021)

LogicExtremist said:


> When you test your RF 14-35mm f/4, can you please compare the uncorrected and software corrected images to confirm the extent of cropping that occurs? Thanks


Will do.


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## gruhl28 (Oct 31, 2021)

BBarn said:


> EXIF data shows the corrected image sizes of both RAW and JPG (large) files taken with the RF 16mm f/2.8 match the full sensor pixel count.


Thanks. So the image is being upscaled. How is the sharpness before vs. after correction?


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## BBarn (Nov 1, 2021)

Here's a quick shot with an RP using the RF 16mm (processed in DPP).




I'm just getting started with PS Elements so I could easily be doing something wrong, but below are two lower right corner areas from the same pic. The first is a JPG from Canon DPP (which automatically applies distortion correction). The second is of the approximately the same area from Photoshop Elements (which was uncorrected). I assume the brightness/contrast/color differences are from the different JPG engines. I don't see much difference in sharpness, but I'll leave that to others.

DPP (corrected)



Photoshop Elements (uncorrected)



Even though the 100% crops are of the same area, the DPP crop is 600x600 pixels, and the PSE crop is 433x433 pixels.


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## Frodo (Nov 1, 2021)

A DPReview subscriber (crusliq) posted some images taken with the RF 16mm on an EOS R. Although not shot at infinity they give a sense of the degree of correction undertaken to remove barrel distortion. All @ f/2.8.
The first is the uncorrected image 6720 x 4480 pixels
In the second I applied +100 distortion correction in Lightroom.
The third is cropped such that the full vertical image is retained. This is 4994 x 3329 pixels or 16.6 MP, compared to 30.1 MP for the uncorrected image.
While this may be okay for an R5, the R6 is left with a little more than 11MP before the image is upscaled. I presume that this also applies for in-Camera corrections.


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## HMC11 (Nov 1, 2021)

neuroanatomist said:


> Will do.


There's another review (https://admiringlight.com/blog/review-canon-rf-14-35mm-f-4l-is-usm/) which indicated that the distortion became mild to moderate by 16mm. Here's his take:

"Thankfully, the distortion is really only truly severe at the 14mm setting. By 15mm, there is still a lot of barrel distortion, and the image circle is just barely not large enough, but by 16mm, the distortion is only mild to moderate and there are no truly dark corners. The mild barrel distortion persists through about 20mm, but by 24mm, the lens is essentially distortion free, before exhibiting a slight pincushion distortion at 35mm. Despite the absolutely severe distortion shown at 14mm, for most of the range, distortion control is pretty good."

Treating this as essentially a ligher & smaller RF 16-35 f4 with the added bonus of fairly usable 14-15mm FoV images might make it easier to go for this lens.

Eagerly awaiting your test results.


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## LogicExtremist (Nov 1, 2021)

Frodo said:


> A DPReview subscriber (crusliq) posted some images taken with the RF 16mm on an EOS R. Although not shot at infinity they give a sense of the degree of correction undertaken to remove barrel distortion. All @ f/2.8.
> The first is the uncorrected image 6720 x 4480 pixels
> In the second I applied +100 distortion correction in Lightroom.
> The third is cropped such that the full vertical image is retained. This is 4994 x 3329 pixels or 16.6 MP, compared to 30.1 MP for the uncorrected image.
> ...


It looks like theres a definite crop, warping and upscaling required to deliver a usable software-corrected image on the RF 16mm f/2.8.


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## LogicExtremist (Nov 1, 2021)

I think I found the RF 16mm f/2.8 lens equivalent EF lens in terms of specs and performance, but it's an EF-S lens...

*Canon RF 16mm F2.8 STM* @ f/8 on an R5 vs *Canon* *EF-S 10-18mm f/4.5-5.6 IS STM* @ 10mm f/4.5 on a 7D Mark II

Equivalent focal length and aperture comparison, with a some very major advantages in favour of the RF lens - RF prime on 2020 release 45MP full-frame sensor vs EF-S zoomon 2014 release 20.2MP APSC sensor.









Canon RF 16mm F2.8 STM Lens Image Quality


View the image quality delivered by the Canon RF 16mm F2.8 STM Lens using ISO 12233 Resolution Chart lab test results. Compare the image quality of this lens with other lenses.




www.the-digital-picture.com





Even with this test skewed heavily in favour of the RF 16mm, can anybody spot a difference in image quality?
The centre sharpness is hard to call, may be sharper on the RF 16mm, mid-frame is a close call, but the EF-S lens appears to be sharper and have better contrast in the periphery to me.


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## gruhl28 (Nov 1, 2021)

Frodo said:


> A DPReview subscriber (crusliq) posted some images taken with the RF 16mm on an EOS R. Although not shot at infinity they give a sense of the degree of correction undertaken to remove barrel distortion. All @ f/2.8.
> The first is the uncorrected image 6720 x 4480 pixels
> In the second I applied +100 distortion correction in Lightroom.
> The third is cropped such that the full vertical image is retained. This is 4994 x 3329 pixels or 16.6 MP, compared to 30.1 MP for the uncorrected image.
> ...


Wow, that's even more being cropped out than previously reported.


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## Czardoom (Nov 1, 2021)

Wow, we probably have never seen such amazing analysis and page long essays regarding the auto-correction of a lens!

Thank goodness, as a photographer, all I care about is the final image. If the Digital Picture's Image comparison tool is reasonably accurate, and the corners are indeed considerably better than the EF 17-40L and not too much worse than the EF 16-35L, then that is good enough for me.

Just curious, but to all those that are despairing about the auto-correction, do you not do any distortion correction in post-processing? Keystone or perspective corrections? Do you ever use the new image enlarging programs (such as GigaPixel) or comands in Photoshop or any other software? Those enlargement programs or commands create a great deal of new pixels, does that mean you won't use them? Or does doing the same thing the camera does on your computer make you forget all about your concerns?


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## RexxReviews (Nov 1, 2021)

victorshikhman said:


> Wasn't the RF mount supposed to allow easier engineering of better designs without these optical weaknesses? Watching this review, the way the focus sounds like the original nifty fifty... It feels like they just slapped this together for lowest possible cost.
> 
> Meanwhile, I'm kicking myself. Two years ago I had a chance to purchase a 24-70 F/4 for $550, and I thought... meh, that's kinda pricey. Now it's going for $1200 on ebay from reputable places. The 16-35 F/4 is also skyrocketing. Maybe supply disruptions are a part of this, but there's still so much demand in good EF lenses, and they're optically no worse than the RF versions. Is Canon leaving money on the table?


What do you consider "sky rocketing"? I just picked up another 16-34 f4 about a month ago for around $700 in mint condition, new its still at the same retail price of around 1099. I have purchased many of this lens in the last few years as its what we use on our real estate training cameras and the only time I've seen them under $600 were usually very heavily used lenses and every blue moon a good shaped one that someone was selling far lower than they realized on FB marketplace.


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## RexxReviews (Nov 1, 2021)

gruhl28 said:


> Wow, that's even more being cropped out than previously reported.


People are not taking in consideration that the lens is shooting much wider than 16mm so that the corrected version is at around 16mm. I have tested this against my 16-35 f4. The corrected RF16mm is even a tad wider than the 16mm of the 16-35


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## neuroanatomist (Nov 1, 2021)

RexxReviews said:


> People are not taking in consideration that the lens is shooting much wider than 16mm so that the corrected version is at around 16mm. I have tested this against my 16-35 f4. The corrected RF16mm is even a tad wider than the 16mm of the 16-35


But if the RF 16/2.8 is giving you a much lower MP image that is then being upscaled, to me that's a concern.


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## Frodo (Nov 1, 2021)

Czardoom said:


> Just curious, but to all those that are despairing about the auto-correction, do you not do any distortion correction in post-processing? Keystone or perspective corrections? Do you ever use the new image enlarging programs (such as GigaPixel) or comands in Photoshop or any other software? Those enlargement programs or commands create a great deal of new pixels, does that mean you won't use them? Or does doing the same thing the camera does on your computer make you forget all about your concerns?


That is the entire point. Take astro photography. This involves a lot of image manipulation, stacking, compositing. If I start with a 20 or 30 MP file that is "clean" out of the camera, I have much more scope for subsequent processing than one which has had such heavy preprocessing.
It is clear that I am asking more than this relatively cheap lens (its still USD500 in New Zealand) can deliver. Probably fine for lots of other photographers.


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## LogicExtremist (Nov 1, 2021)

Czardoom said:


> Wow, we probably have never seen such amazing analysis and page long essays regarding the auto-correction of a lens!
> 
> Thank goodness, as a photographer, all I care about is the final image. If the Digital Picture's Image comparison tool is reasonably accurate, and the corners are indeed considerably better than the EF 17-40L and not too much worse than the EF 16-35L, then that is good enough for me.
> 
> Just curious, but to all those that are despairing about the auto-correction, do you not do any distortion correction in post-processing? Keystone or perspective corrections? Do you ever use the new image enlarging programs (such as GigaPixel) or comands in Photoshop or any other software? Those enlargement programs or commands create a great deal of new pixels, does that mean you won't use them? Or does doing the same thing the camera does on your computer make you forget all about your concerns?


As far as I know all lenses use distortion correction, that's not the issue. What is catching peoples attention here is the crazy amount of distortion of this lens that is only possible because it's being used on a mirrorless system, which can hide it because it does on-the-fly image correction when looking through the EVF and makes the same corrections in camera when shooting JPEG images. This level of distortion would never be seen on a DSLR with an OVF, as it would produce a severely warped image viewing through the lens.

The are three main problems:

The lens has heavy vignetting, the corners of the uncorrected image are pure black, so no amount of shadow recovery will bring those details back. As such, they need to be cropped away, which by most estimates is thought to remove around 30% of the pixels! Rather than create a smaller cropped image, the software then upscales the image digitally back to full size, so 1/3 of the pixels are just made up. This is like digital zoom on a smartphone and on point-and-shoot cameras.
The uncorrected image is extremely warped, that it requires extreme correction, so in some places, pixels need to be squeezed closer together (are multiple pixels averages and then thrown out?), and in other places, like the corners, they need to be stretched further apart to create a rectilinear shape. Pixels don't stretch, so the spaces need to be filled in with extra pixels of fake computer-generated data, which the computer can't possibly predict, so it uses a formula to guess what they might be from surrounding pixels, so the detail in the corners will look soft and mushy.
When the cropped image with fake pixels in the corners is upscaled, it is filled with computer generated pixels right through the image. The corners which are already degraded and soft from being filled with fake data pixels are then also digitally enlarged and filled a second time with more fake data, degrading them even further.

Simply put, the reason why photographers are advised not to go too heavy handed with post-processing is because image quality can start to fall apart, and detail can be lost. To produce usable images, two post-processing operations need to be performed at an extreme level with this lens just to get a usable image that we can start working on.

Earlier in this thread, I compared the Rf 16mm to the equivalent APSC lens, the EF-S 10-18mm, and this old crop sensor lens has very little distortion by comparison, as shown here:








Here's the lens distortion of the RF 16mm f/2.8 for the Christopher Frost video:




One important point that everyone has probably missed here is that test charts shot in RAW don't have any post processing applied to them other than lens corrections. Real images will have additional post-processing applied, sometimes a bit, sometimes quite a lot, and when they're applied over really extreme previous post-processing changes, the images simply don't hold up.

Comparing test charts and using image test tools like I've posted in this thread don't give an objective and accurate picture of how the software corrections affect real world images. It would be interesting to see a comparison of two identical landscape images, one taken on the RF 16mm f/2.8, and one on another 16mm (that doesn't use the radical software corrections), both taken through the complete workflow to produce the final photo, to see how the end result looks!


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## RexxReviews (Nov 2, 2021)

Here are some samples I have been playing with. These have been shot on the R5

The first is from my 16-35 f4. This is with the LR profile.




This is with the RF 16mm. This is a .jpg directly from camera using the built in camera corrections. The built in camera crop is Pretty much the same as the 16-35 @16mm




This is the RAW of the same photo directly above with my manual corrections in LR. RF 24-240mm Profile . 130 Distortion. +100 Vignetting and 11 Midpoint in the manual tab.


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## gruhl28 (Nov 2, 2021)

RexxReviews said:


> Here are some samples I have been playing with. These have been shot on the R5
> 
> The first is from my 16-35 f4. This is with the LR profile.
> 
> ...


Thanks for the samples! The 16-35 seems to show a slightly wider FOV than the 16 mm jpg (see the right side of the image; the left side lines up identically but there is more visible on the right), and the Raw image with the correction from the 24-240 shows a much wider FOV than either of the two previous images.


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## gruhl28 (Nov 2, 2021)

One interesting thing about the 16mm, which I think someone earlier made reference to, is that stopping down seems to have virtually no effect on image quality other than vignetting. See https://www.the-digital-picture.com...eraComp=1508&SampleComp=0&FLIComp=0&APIComp=4


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## LogicExtremist (Nov 2, 2021)

gruhl28 said:


> One interesting thing about the 16mm, which I think someone earlier made reference to, is that stopping down seems to have virtually no effect on image quality other than vignetting. See https://www.the-digital-picture.com...eraComp=1508&SampleComp=0&FLIComp=0&APIComp=4


That was me!  Yes, that's correct, corner sharpness doesn't improve when stopping down like regular lenses do because the corners are streched out and digitally filled with fake pixels to make up what the optics never captured in the first place!


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## RexxReviews (Nov 2, 2021)

Its really starting to feel like this is going to turn into more of a "YouTuber" "Vlogger" lens than anything else as the video seems decent on it for the price. I think those of us hoping to do more with it from a photog point of view are just going to be out of luck. We were REALLY hoping to be able to use this lens for real estate on our training camera due to the size and weight vs the 16-35's.


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## BBarn (Nov 2, 2021)

LogicExtremist said:


> ... corner sharpness doesn't improve when stopping down like regular lenses do because the corners are streched out and digitally filled with fake pixels to make up what the optics never captured in the first place!


 
The uncorrected geometric distortion of the RF 14-35 is similar to that of the RF 16. Yet, geometric distortion correction of the RF 14-35 yields very good corner sharpness. That would not be the case if geometric correction inherently introduced significant softness to an image. As I said before, if you really want to understand why the RF 16 is soft in the corners, look somewhere besides geometric distortion correction.

My own observations of pics I've taken with the two lenses show that geometric correction isn't highly destructive to image sharpness. And while the corrected corners of the RF 16 are softer than the RF 14-35, they are still quite acceptable for a majority of uses. It's not like corrected corners of the RF14-35 are merely adequate, and those of the RF 16 are hideous. Far from it.


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## koenkooi (Nov 2, 2021)

BBarn said:


> The uncorrected geometric distortion of the RF 14-35 is similar to that of the RF 16. Yet, geometric distortion correction of the RF 14-35 yields very good corner sharpness. That would not be the case if geometric correction inherently introduced significant softness to an image. As I said before, if you really want to understand why the RF 16 is soft in the corners, look somewhere besides geometric distortion correction.
> 
> My own observations of pics I've taken with the two lenses show that geometric correction isn't highly destructive to image sharpness. And while the corrected corners of the RF 16 are a bit softer than the RF 14-35, they are still quite acceptable for a majority of uses. It's not like corrected corners of the RF14-35 are merely adequate, and those of the RF 16 are hideous. Far from it.


Agreed, the RF16 outperforms my EF17-40L in the corners, which is exactly what I bought it for.


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## Frodo (Nov 3, 2021)

I took the same raw files that I posted about just above:
- Applied the profile for the RF24-240: This is quite an improvement on the uncorrected image, but is not quite there. Interestingly, Lightroom shows the same file dimensions as the uncorrected file. Does the profile upscale the cropped image?
- Added +25 distortion correction in Lightroom. This now matches my earlier corrected image, but the image file is 6204x4136 pixels . This is 25.6 MP or 85% of original resolution. I could live with this.

I also applied the LR profile for my Samyang 14mm f/2.8. This also generates the full resolution, in spite of being cropped.
I didn't know that LR profiles upscaled cropped files.


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## gruhl28 (Nov 3, 2021)

Frodo said:


> I took the same raw files that I posted about just above:
> - Applied the profile for the RF24-240: This is quite an improvement on the uncorrected image, but is not quite there. Interestingly, Lightroom shows the same file dimensions as the uncorrected file. Does the profile upscale the cropped image?
> - Added +25 distortion correction in Lightroom. This now matches my earlier corrected image, but the image file is 6204x4136 pixels . This is 25.6 MP or 85% of original resolution. I could live with this.
> 
> ...


Thanks for the new examples. Since Lightroom is non-destructive, I wasn't surprised that the pixel count didn't change after applying a profile. I see the same behavior on other lenses. But then why did the count change after applying the +25? I tried this with a shot on another lens, and a manual distortion correction also didn't change the pixel count. Only after manually applying a crop did the Cropped dimensions change.


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## Frodo (Nov 4, 2021)

gruhl28 said:


> Thanks for the new examples. Since Lightroom is non-destructive, I wasn't surprised that the pixel count didn't change after applying a profile. I see the same behavior on other lenses. But then why did the count change after applying the +25? I tried this with a shot on another lens, and a manual distortion correction also didn't change the pixel count. Only after manually applying a crop did the Cropped dimensions change.


Sorry, I should have clarified: I cropped the second image after applying the distortion correction.


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## LogicExtremist (Nov 4, 2021)

BBarn said:


> The uncorrected geometric distortion of the RF 14-35 is similar to that of the RF 16. Yet, geometric distortion correction of the RF 14-35 yields very good corner sharpness. That would not be the case if geometric correction inherently introduced significant softness to an image. As I said before, if you really want to understand why the RF 16 is soft in the corners, look somewhere besides geometric distortion correction.
> 
> My own observations of pics I've taken with the two lenses show that geometric correction isn't highly destructive to image sharpness. And while the corrected corners of the RF 16 are softer than the RF 14-35, they are still quite acceptable for a majority of uses. It's not like corrected corners of the RF14-35 are merely adequate, and those of the RF 16 are hideous. Far from it.


The explanation is quite simple, the better optics in the RF 14-35mm resolve much more detail, so you start off with a more detailed warped image than the RF 16mm. After crunching the pixels equally to correct them, the L-series zoom will naturally look better. It can't be anything other than software correction because the corners and periphery don't sharpen when the lens is stopped down, and that's because they're fake pixels, which are just best guess filler-pixels that don't respond to aperture. Real pixels do on the RF 50mm f/1.8, which becomes very sharp across the frame when stopped down to f/5.6 and higher.

You mention that from your own observations using the two lenses, the geometric correction isn't highly destructive to image sharpness and the corners aren't too bad. Is that just from a test image? In a real world application of a real estate photo or a landscape shot, additional post-processing is required to turn the raw image with lens corrections into a proper photo. It's not accurate to say the image corners look okay with either lens if the images aren't subjected to the regular post-processing workflow.

The test is easy, for a quick landscape shot just crank up the lens aperture to say f/8 to f/11 for a good FOV and to eliminate wide aperture blur in the corners, put the camera on a tripod and take an outdoor shot, then post-process to get as much details out of the shadows and highlights, make any other adjustments so it looks good to your eye, then analyze the final image. If real-estate style photography is preferred, do what needs to be done there to get the angles and perspective right in a room, and avoid blown out highlights from light through windows using HDR or accurate exposure comp and detail recovery, and see how it looks. We're just emulating real world use.

When it comes to raw images with only lens corrections applied, anyone can get decent images using an entry level camera with a kit lens. To produce anything beyond SOOC JPEG quality, the images need to be pushed a bit further in post processing, and that's when the shortcomings of the lens and body begin to show.

Simply put, the only way to properly evaluate these lenses is to put the raw images through a complete post-processing workflow, like what would happen in real-world use, and then check to see how the corner details hold up. Then we can say wheter thre final images look okay or not, and then we can make an informed decision as too whether the quality is good enough for purpose or not for each individual. If shooting JPEGs then it won't make a difference as there's not post processing carried out on what comes out of the camera. If I had either lens I'd happily test it out for everyone, but I don't, I can't...


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## gruhl28 (Nov 4, 2021)

LogicExtremist said:


> The explanation is quite simple, the better optics in the RF 14-35mm resolve much more detail, so you start off with a more detailed warped image than the RF 16mm. After crunching the pixels equally to correct them, the L-series zoom will naturally look better. It can't be anything other than software correction because the corners and periphery don't sharpen when the lens is stopped down, and that's because they're fake pixels, which are just best guess filler-pixels that don't respond to aperture. Real pixels do on the RF 50mm f/1.8, which becomes very sharp across the frame when stopped down to f/5.6 and higher.
> 
> You mention that from your own observations using the two lenses, the geometric correction isn't highly destructive to image sharpness and the corners aren't too bad. Is that just from a test image? In a real world application of a real estate photo or a landscape shot, additional post-processing is required to turn the raw image with lens corrections into a proper photo. It's not accurate to say the image corners look okay with either lens if the images aren't subjected to the regular post-processing workflow.
> 
> ...


I agree that the way to evaluate whether the lens meets someone's needs is to take an image similar to those usually taken and then post-process in the way that one usually does. However, I disagree that post-processing is necessarily going to degrade the image further and make it look worse. Things like noise often get worse, but I don't see why a lack of sharpness would necessarily get worse. Of course, the only way to know is to actually try it.

I'm also not sure about your explanation of why the image doesn't improve with stopping down. These aren't completely "fake" pixels constructed out of nothing. Even if new pixels are being created, they are being created based on the pixels that were there before corrections. So if the actual image gets sharper when stopping down, then the corrected image based on the stopped down results should be sharper also. You rightly pointed out that the 14-35 resolves much more detail to begin with, and so the corrected image also shows more detail. That same logic would apply to stopping down; if the actual image coming from the lens improves, then the corrected image should also be improved. I'm not saying that the large distortion corrections might not be contributing to the apparent lack of improvement upon stopping down, but I don't think this can be the entire reason. Not all lens aberrations improve with stopping down. Out of curiosity I looked at the 14-35 results when stopping down, and I admit that these also don't seem to really improve (apart from vignetting of course), although there isn't a lot of room for improvement in that lens to begin with - the results are pretty good even wide open.

It would be interesting to hear from someone from Canon (which probably isn't going to happen) or someone else with real expertise in lens design and processing, who could explain fully what is happening here. We are all taking educated guesses, but I'd love to hear a complete explanation from someone who really knows what is happening and why we are seeing the results we're seeing.


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## LogicExtremist (Nov 4, 2021)

gruhl28 said:


> I agree that the way to evaluate whether the lens meets someone's needs is to take an image similar to those usually taken and then post-process in the way that one usually does. However, I disagree that post-processing is necessarily going to degrade the image further and make it look worse. Things like noise often get worse, but I don't see why a lack of sharpness would necessarily get worse. Of course, the only way to know is to actually try it.
> 
> I'm also not sure about your explanation of why the image doesn't improve with stopping down. These aren't completely "fake" pixels constructed out of nothing. Even if new pixels are being created, they are being created based on the pixels that were there before corrections. So if the actual image gets sharper when stopping down, then the corrected image based on the stopped down results should be sharper also. You rightly pointed out that the 14-35 resolves much more detail to begin with, and so the corrected image also shows more detail. That same logic would apply to stopping down; if the actual image coming from the lens improves, then the corrected image should also be improved. I'm not saying that the large distortion corrections might not be contributing to the apparent lack of improvement upon stopping down, but I don't think this can be the entire reason. Not all lens aberrations improve with stopping down. Out of curiosity I looked at the 14-35 results when stopping down, and I admit that these also don't seem to really improve (apart from vignetting of course), although there isn't a lot of room for improvement in that lens to begin with - the results are pretty good even wide open.
> 
> It would be interesting to hear from someone from Canon (which probably isn't going to happen) or someone else with real expertise in lens design and processing, who could explain fully what is happening here. We are all taking educated guesses, but I'd love to hear a complete explanation from someone who really knows what is happening and why we are seeing the results we're seeing.


The way software lens correction and post-processing works is by performing mathematical operations on the pixel data. It's not possible to create accurate pixel data that was never captured optically, as the software can't tell what's being photographed, it uses and algorithm to try guess the pixels from those around it. If one software operation calculates pixels, then another operation applied over that also uses those calculated pixels to generate new calculated pixels, then there is the potential to generate garbage data, which appears as aberrations, which are commonly seen in over-processed images, where things appear in the image that never existed in real life. Depending on the image post-processing workflow operation, this might or might not be a problem, will vary on a case-by-case basis and is easy to test. 

To quote the following review of the lens _"Distortion correction is destructive at the pixel level as some portion of the image must be stretched or the overall dimensions reduced. " _









Canon RF 16mm F2.8 STM Lens Review


Is the Canon RF 16mm F2.8 STM Lens right for you? Learn all you need to know in The-Digital-Picture.com's review!




www.the-digital-picture.com





_"This is an upper-left quadrant of an f/2.8 image, the misshapen circles seem to correlate with the distortion corrected area of the frame. "_







You can see the distortion correction is turning the sharp circles in the image into blurred ovals in the left hand top corner. Performing further post-processing on these might create something even more random.

My understanding of why the corners don't sharpen at higher apertures is as follows:

The RF 16mm is optically sharp in the centre, and that part isn't being software corrected as much as the optically soft corners, which are being blurred more by fake data pixel filling. 
Stopping down the aperture to sharpen the image is *optical *in nature. 
Software corrected pixels in the corner are *computer generated* and can't be improved by changing aperture.

If anyone has a better theory, I'm curious to hear it!


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## LogicExtremist (Nov 4, 2021)

RexxReviews said:


> Here are some samples I have been playing with. These have been shot on the R5
> 
> The first is from my 16-35 f4. This is with the LR profile.
> 
> ...


The image isn't that great unfortunately considering we want to compare corner sharpness! If you could stop down both lenses to f/8 and place something with fine detail in each lower corner, such as a box or book with fine lettering, that would tell us heaps. Interesting that the EF 16-35mm f/4 L is wider than the RF 16mm f/2.8. Thanks


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## stevelee (Nov 4, 2021)

neuroanatomist said:


> I am pretty sure that if Canon labels a lens 16mm or 14mm, the FoV delivered in the final images will be that. Keep in mind that focal length is specified at infinity focus. Since people testing for lens distortion aren’t using charts or walls large enough to fill the frame with the lenses focused at infinity, focus breathing must be considered. For example, the EF-S 18-200mm at the long end frames at ~150mm equivalent with a close subject, the EF 100/2.8L Macro frames like ~67mm at 1:1. The 16/2.8 probably has a fair bit of breathing, the 14-35 less so.


It would be helpful if someone would send a giant test chart into orbit.


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## Frodo (Nov 6, 2021)

Interesting video here where the guy looks at the RF 16mm for astrophotography. He concludes that it is usable, although not as sharp as the EF 16-35mm f/4. Coma and vignetting quite severe in the corners, but he cropped to the same FOV as the 16-35 and much of this disappeared.
I wonder what a raw processed in DPP exported as tif to Photoshop or Lightroom would look like.


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## Czardoom (Nov 6, 2021)

LogicExtremist said:


> As far as I know all lenses use distortion correction, that's not the issue. What is catching peoples attention here is the crazy amount of distortion of this lens that is only possible because it's being used on a mirrorless system, which can hide it because it does on-the-fly image correction when looking through the EVF and makes the same corrections in camera when shooting JPEG images. This level of distortion would never be seen on a DSLR with an OVF, as it would produce a severely warped image viewing through the lens.
> 
> The are three main problems:
> 
> ...


All I know is that Olympus,. Sony and others have been doing this for a few years now. No one who uses those lenses is creating the kind of hysteria that is being created on this thread. I own the Olympus 12-100mm f/4 - a lens with very heavy distortion correction automatically applied. Feel free to read all the reviews of that lens you want - or I'll save you the trouble - it is very highly regarded as a Pro quality lens. 

You talk of the "black pixels" in the corners that can't be recovered. Not supposed to be, after correction they are beyond the frame. So, yes, pixels are being stretched. Interpolations are being made. Exactly what happens when you or I or most photographers use distortion correction when post processing. Or use Ketstone or perspective correction.

You write, "Pixels don't stretch, so the spaces need to be filled in with extra pixels of fake computer-generated data, which the computer can't possibly predict..."

Guess what, yes the computer can. It does it all the time. How about Gigapixel or Photoshop's new enlargent application. Good heavens I just used Gigapixel that doubled my pixel count. All those made up pixels - it must be a disaster. But, no actually. Looks pretty good.

Yes, some interesting facts have been presented regarding how much distortion, and and an estimate of many MP's are lost in the process. But this thread has gone way beyond that into "fake pixels" and other hysteria that is actually somewhat amusing to those of use (or at least to me) who have used the Olympus lens and others like it. 

Canon's mistake is not that use auto-correction, their mistake is that they didn't make sure that every photo processing software had the profiles in advance. Then we would be spared all the analysis of un-processed photos that we will never see once the profiles are in place. 

It's a $300 lens and by most or all accounts I have read, it done a pretty good job - out performinig the 17-40 L lens, for example. That, it seems to me, is the most important "fact".


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## LogicExtremist (Nov 7, 2021)

Czardoom said:


> All I know is that Olympus,. Sony and others have been doing this for a few years now. No one who uses those lenses is creating the kind of hysteria that is being created on this thread. I own the Olympus 12-100mm f/4 - a lens with very heavy distortion correction automatically applied. Feel free to read all the reviews of that lens you want - or I'll save you the trouble - it is very highly regarded as a Pro quality lens.
> 
> You talk of the "black pixels" in the corners that can't be recovered. Not supposed to be, after correction they are beyond the frame. So, yes, pixels are being stretched. Interpolations are being made. Exactly what happens when you or I or most photographers use distortion correction when post processing. Or use Ketstone or perspective correction.
> 
> ...



You do realise that "they're doing it, so that makes it okay to do it too" is not a sound argument, that's the bandwagon fallacy, it's a logical fallacy which just appeals to popularity. My response would simply be that if Canon, who are known for the quality of their lenses, take the same shortcuts that Sony does (I'm trusting your claim on this, not sure how true it is), then that's one less reason to choose Canon over Sony.

Software correction is not all the same as you probably already can figure. To use an extreme example just to illustrate a point, stretching a triangle of pixels into a square is much harder, will generate more fake data, and degrade an image more than than simply making a square of pixels twice as large. Similarly, stretching out corners requires more pixels generated, and is less precise than an interpolation of a uniformly sharp image to make it twice as large.

You've proven my point with your example, images enlarged with Topaz Gigapixel look amazing, while the software generated corners in the RF 16mm f/2.8 look soft, blurry and smeared. The proof is in the results, the final images, and that's what matters when producing photos.

Incidentally, there's no hysteria here, just an objective evaluation of what the lens can and can't do, without any attempted rationalisation to make excuses for its shortcomings. What we're discussing is why the corners look like crap, and we more or less know why from this discussion and others.

If we need a lens or a specific purpose, then it will either work or it wont, regardless of whether the brand is a Canon, Sony or Olympus. Knowing the shortcomings of a lens helps buyers make informed decisions in respect to their specific needs.

When we consider what 16mm primes are generally used for, we can draw reasonable conclusions from the reviews and discussions about how this lens performs in each of these areas:

Architecture/interiors - no
Landscape - no
Astro - no/maybe
General video - yes
Vlogging - yes
Webcam - yes
Travel/hiking - yes

Does this not sound reasonable?


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## LogicExtremist (Nov 7, 2021)

It's strange seeing people wishing that a lens is something more than it is!

What does Canon say the Rf 16mm f/2.8 is for?

Let's look at the advertising from Canon's websites in The US, UK and Australia, noting the difference in features emphasized.

-----------------------------

The *Canon US* website oversells this lens in terms of vague, non-specific sales hype as expected:

"Compact, versatile, speedy and affordable, the new RF16mm F2.8 STM lens is a terrific complement to any EOS R series digital camera. Offering an ultra-wide angle of view and a bright f/2.8 aperture, it's an excellent choice whether taking interior photos in tight spaces, seeking out the perfect landscape, or as the perfect webcam lens when used in combination with an EOS camera and EOS Webcam Utility on a video call. With a 16mm F2.8 lens, you can experiment with enhancing perspectives, capturing starscapes, or with the close focusing distance of 5.11 inches, get up close to your subject while still keeping the background more visible. Video users will find this ultra-wide lens a natural for vlogging, especially with its supremely light weight. With its remarkable combination of optical excellence and refined performance, all in a small package that's easy to bring most anywhere, the RF16mm F2.8 STM is a stellar companion to any EOS R series digital camera."

-----------------------------

The* Canon UK *website states:

"Put yourself in the picture with this fast, affordable, ultra-wide EOS R-series lens. At 16mm this full frame prime is great for vlogging, landscapes, architecture, astrophotography and more."

The very first feature headlined is this:

*Go wide, go bright and put yourself in the picture*

Meet the RF 16mm F2.8 STM. It’s the ultimate affordable EOS R-series lens for vlogging and more.

*Designed for vloggers and creative content makers
*
For crisp, clear ultra-wide views this lightweight and super compact full frame 16mm prime will transform your images and videos, inspiring creativity at every opportunity – from landscapes to architecture and even astrophotography. Can you afford not to have one?

-----------------------------

The *Canon Australia* site has a more honest description of its product:

*The perfect wide-angle addition to your kit*

The RF 16mm f2.8 STM is the first ultra-wide fixed focal length lens in the RF line up. This compact and lightweight lens is perfect for getting bright, panoramic landscapes to fun portraits and videos.

*Versatile wide angle lens, the perfect travel companion*
Image of the beach with trees taken with the RF 16mm F2.8 STM wide angle lens

The ultra-wide 16mm lens is a perfect addition to your kit while travelling, allowing you to capture scenic landscapes to large group shots and selfies.

-----------------------------

As we can see, Canon UK puts the emphasis on its use as a vlogging lens, while Canon Australia highlights its use as a travel lens. In advertising, just like in ingredients list, the most important things are listed first. Quite telling really...


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## LogicExtremist (Nov 7, 2021)

Here's a good video that explains the strengths and weaknesses of the RF 16mm f/2.8 quite well:


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## BBarn (Nov 7, 2021)

I'm sure many owners like myself are finding the RF 16mm to be a great little lens, with performance commensurate with the price. One shouldn't expect top notch "L" level performance at a fraction of the price. I also suggest that those never having used the lens avoid establishing their own narrative for the lens.


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## LogicExtremist (Nov 7, 2021)

BBarn said:


> I'm sure many owners like myself are finding the RF 16mm to be a great little lens, with performance commensurate with the price. One shouldn't expect top notch "L" level performance at a fraction of the price. I also suggest that those never having used the lens avoid establishing their own narrative for the lens.


I'd say that nobody is reasonably expecting L-series lens performance from this lens. I doubt that anyone would question this lens as being great value for money, it's Canon's second cheapest budget prime, and it's quite a fast lens for an ultrawide with an aperture of f/2.8. 

We all understand that budget lenses have their shortcomings, and by knowing what these are, potential buyers can make informed decisions. I don't believe anyone is questioning the choice of the people who bought this lens, as everyone will have different reasons for choosing it and different requirements when using it. 

It's evident that the corners are blurry, that's a fact, but they may be good enough for some uses, and blurry corners don't matter in some genres of photography, but can be deal-breakers in others. That just means this lens might be fine for some photographers, and not others, no big deal...

What matters, and what potential buyers need, is more user information shared to either support the finding of the reviews, or bring in new information. Unless a person just collects camera gear, a specific focal length will be used for a particular purpose in mind, and an UWA 16mm on full frame is more of a niche focal length for very specific uses, unlike a more universal 24mm lens. Anyone considering buying one will want to know how well it does the things it's designed to do. So, from your experience with this lens, if you've run some tests already, it would be great to know what 16mm tasks it performs well, and where you feel it might be lacking. Thanks!


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## BBarn (Nov 8, 2021)

I'm not a lens tester, and have little interest in photographing flat images from a very short distance away with an ultra wide angle lens. I prefer to use a longer lenses for that sort of work. Nor do I have much interest in what an image looks like at 400% when viewed from a foot or so away on a large computer monitor. 

With the above in mind, here's a brief summary of my limited still photography use of the RF 16mm f/2.8 on my EOS RP (so a budget lens on a low [relatively] cost body). I also should note that my comments are based on results from SOOC JPGs and RAW shots processed in Canon DPP (both of which perform lens corrections automatically).

In photos where the closest object to the lens is more than a few feet away, high magnifications appear to show pixelation becoming an issue by the time image quality becomes obviously soft. At lower magnifications like 100%, photos are reasonably sharp anywhere in the frame.

For very close-up images only inches away, differences between center and corner sharpness become more apparent. I find it very challenging to capture dynamic UWA shots that draw the viewer into the photo, images where some of the objects are often only inches away. Finding a good balance of sharpness/depth of field has always proven the most difficult task in capturing those images for me. And finding that good balance generally overshadows limitations of corner sharpness in an UWA lens (for me).

In photographing interior rooms in a house, most objects are more than a few feet away. So most things are rather small as captured with a 16mm lens. And unless the photos are going to be viewed at more than 100% (which is unlikely in most cases) everything will appear acceptably sharp from the RF 16. If you insist on zooming in to 400% and trying to read an open book on the coffee table 10' away, you are probably going to be disappointed.

If capturing outdoor landscapes where most everything of interest is 20+' away, the small size of those objects makes it nearly impossible to capture great detail of those objects, especially with a $300 lens on a 26MP body. So the inability to capture fine detail is going to be driven much more by the small size of the objects than a lack of lens sharpness. Even objects 20+' away in the center of the image where a lens is sharp are going to be too small to capture stunning detail.

I have no experience with astrophotography, so I won't comment on that. And I'm not into video, so I won't address that use either. As far as general use, or hiking/travel, I suppose the lens would work OK. But unless there is an object of interest that one can get real close to, or on top of, the picture from a UWA lens is likely to be boring. So for most of those occasions, I consider a UWA is a poor choice. Using a UWA lens one can surely "get it all in", but in most cases everything will probably be so small the viewer will be left wondering what the subject is (because everything is so small).

I'll also comment on the use of filters. The lens is threaded for 43mm filters. The standard 43mm UV filter I have on the lens does not appear to introduce any additional corner shading. I don't have a standard 43mm Grad or Polarizer to try, so I don't know if they will cut the corners or not. 

If you are thinking about using step-up rings, be careful. There is a small lip on the lens front that extends forward beyond the retracted position of the lens. Any step-up ring 58mm or greater attached directly to the lens will hit that small lip when the lens retracts in the off position. Use of step-up rings in front of an attached UV filter negates that issue, but many photographers don't like to stack filters. A standard thickness 58mm polarizer or similar filter may shade the corners a bit when stacked with a standard 43mm UV filter. But a standard thickness 67mm polarizer or similar filter does not appear to shade the corners when stacked with a standard 43mm UV filter.

The use of "thin" filters obviously can impact the above in a positive way, but I don't know from experience how much of an improvement they might offer.

Overall, the lens is very handy and quite easy and enjoyable to use. Those wanting to photograph printed material a few inches away and/or enjoy searching images at 400% will probably be disappointed in the corner sharpness. Those taking pictures of most other things in typical ways will probably be happy with the lens.


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## neuroanatomist (Nov 8, 2021)

LogicExtremist said:


> When you test your RF 14-35mm f/4, can you please compare the uncorrected and software corrected images to confirm the extent of cropping that occurs? Thanks


Did a quick set of shots last week, but I’m not happy with the execution. Either I wasn’t perfectly orthogonal to my subject or the electronic level in my R is very slightly off. Also, I wanted to compare OOC JPGs as well as processed RAW, but I usually keep in-camera corrections off and I shot the 11-24 like that. Finally, the framing changed slightly between the 14-35 and 11-24 because the weight of the front-heavy 11-24 caused a little ballhead droop. That was with my travel tripod, an RRS TQC-14 with the little BH-30 head. 

So, I’ll try again tomorrow if time permits, and this time I’ll bring my RRS TVC-33 with the beefy BH-55 head, that setup doesn’t move.


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## LogicExtremist (Nov 8, 2021)

neuroanatomist said:


> Did a quick set of shots last week, but I’m not happy with the execution. Either I wasn’t perfectly orthogonal to my subject or the electronic level in my R is very slightly off. Also, I wanted to compare OOC JPGs as well as processed RAW, but I usually keep in-camera corrections off and I shot the 11-24 like that. Finally, the framing changed slightly between the 14-35 and 11-24 because the weight of the front-heavy 11-24 caused a little ballhead droop. That was with my travel tripod, an RRS TQC-14 with the little BH-30 head.
> 
> So, I’ll try again tomorrow if time permits, and this time I’ll bring my RRS TVC-33 with the beefy BH-55 head, that setup doesn’t move.


Thanks! Better to take the time and get results you're happy with.


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## neuroanatomist (Nov 8, 2021)

LogicExtremist said:


> Thanks! Better to take the time and get results you're happy with.


I don't really care if I'm happy with the results or disappointed by them, as long as I'm confident that they were generated in a robust and unbiased manner.


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## LogicExtremist (Nov 8, 2021)

BBarn said:


> I'm not a lens tester, and have little interest in photographing flat images from a very short distance away with an ultra wide angle lens. I prefer to use a longer lenses for that sort of work. Nor do I have much interest in what an image looks like at 400% when viewed from a foot or so away on a large computer monitor.
> 
> With the above in mind, here's a brief summary of my limited still photography use of the RF 16mm f/2.8 on my EOS RP (so a budget lens on a low [relatively] cost body). I also should note that my comments are based on results from SOOC JPGs and RAW shots processed in Canon DPP (both of which perform lens corrections automatically).
> 
> ...


Thanks, this is probably one of the most helpful and informative posts so far on the RF 16mm f/2.8. 

I too have little interest in photographing flat images at any distance with any lens. More interested in real life subject matter viewed at 100% max and glad that's what you shared info on. The Canon RP at 26MP is close to the R and more than the R6, so that gives some idea of the expected resolving power of the lens at the centre.

The observations about lens filters you've provided are extremely handy, as many people like to use some sort of filter with landscape photography. Good to know standard filters don't cause mechanical vignetting and that using a filter under a step-up ring avoids mechanical inteference or the lens barrel when retracted. All UWA lenses can have issues with circular polarising filters, regardless of price, it's just an optical thing where dark patches can appear in certain positions.

You're right, any UWA lens is a specialised lens, and because of the wide field of view, subjects by necessity appear small, and cover less pixels on a sensor, so less details are captured. Most reviewers describe it as a great, affordable, carry-around 'just in case' UWA lens for photographers to add to their camera bag. Appreciate you sharing your experience!

For video, I've noticed from reviews that all UWA lenses can give wobbly "jello" corners in cameras with IBIS, so it's best switched off. Walk and talk style vlogging is way too bouncy without stabilisation though, so some reviewers recommend using the RP or R and their digital image stabilisation instead.


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## LogicExtremist (Nov 8, 2021)

neuroanatomist said:


> I don't really care if I'm happy with the results or disappointed by them, as long as I'm confident that they were generated in a robust and unbiased manner.


That's what I meant, that you're happy with the objectivity of the results, not the aesthetics lol!


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## neuroanatomist (Nov 10, 2021)

Frodo said:


> A DPReview subscriber (crusliq) posted some images taken with the RF 16mm on an EOS R. Although not shot at infinity they give a sense of the degree of correction undertaken to remove barrel distortion. All @ f/2.8.
> The first is the uncorrected image 6720 x 4480 pixels
> In the second I applied +100 distortion correction in Lightroom.
> The third is cropped such that the full vertical image is retained. This is 4994 x 3329 pixels or 16.6 MP, compared to 30.1 MP for the uncorrected image.
> ...


I'm in the midst of processing a series of shots taken with the RF 14-35/4, and it appears to me that the above test is flawed. When performing a manual correction for barrel distortion, dragging the ACR slider to +100 does not equate to correcting 100% of the distortion. Rather, the slider is merely an arbitrary scale of 100 units of correction in the (+) direction for correcting barrel distortion or in the (–) direction for correcting pincushion distortion. In other words, +100 is likely too much correction. In the case of the 14-35mm at 14mm, around +40 does a _reasonable_ job of correcting the rather severe barrel distortion.

The other point is that it's a _reasonable_ job. Manual distortion correction assumes the characteristic of the distortion is linear (along the image radial), and that's almost never going to be the case. So, if you drag the distortion correction slider to the point where horizontal lines in the corners of the scene appear horizontal in the image, then there is residual barrel distortion of lines in the mid-frame. Conversely, if you drag the distortion correction slider to the point where horizontal lines in the mid-frame of the scene appear horizontal in the image, pincushion distortion of lines in the corners is introduced. Basically, manual distortion correction is applying a linear process to a non-linear aberration.

That's where lens profiles come into play. Applying the lens profile for the 14-35/4 in ACR results in horizontal lines in both the corners and the mid-frame appearing horizontal in the image, i.e. the profile includes a non-linear correction for distortion. The same can be achieved in Photoshop using a warp transform, for example. Doing so does 'stretch' the corners of the image, so in that sense there are 'fake pixels' being created, but it allows geometric correction without the need to crop then upscale the image. In the case of an even more complex distortion (e.g. mustache) a warp-type transformation is really the only way it can be corrected. 

More to come.....


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## LogicExtremist (Nov 11, 2021)

neuroanatomist said:


> I'm in the midst of processing a series of shots taken with the RF 14-35/4, and it appears to me that the above test is flawed. When performing a manual correction for barrel distortion, dragging the ACR slider to +100 does not equate to correcting 100% of the distortion. Rather, the slider is merely an arbitrary scale of 100 units of correction in the (+) direction for correcting barrel distortion or in the (–) direction for correcting pincushion distortion. In other words, +100 is likely too much correction. In the case of the 14-35mm at 14mm, around +40 does a _reasonable_ job of correcting the rather severe barrel distortion.
> 
> The other point is that it's a _reasonable_ job. Manual distortion correction assumes the characteristic of the distortion is linear (along the image radial), and that's almost never going to be the case. So, if you drag the distortion correction slider to the point where horizontal lines in the corners of the scene appear horizontal in the image, then there is residual barrel distortion of lines in the mid-frame. Conversely, if you drag the distortion correction slider to the point where horizontal lines in the mid-frame of the scene appear horizontal in the image, pincushion distortion of lines in the corners is introduced. Basically, manual distortion correction is applying a linear process to a non-linear aberration.
> 
> ...



I did bit of a search and fount that Dustin Abbott's review of the Canon RF 14-35mm F4L IS USM lens supports your findings:

_"The distortion is extremely heavy; it required a +34 to achieve this manual correction, and it is also is not linear, so that results in a “mustache” pattern left behind. The standard correction profile obviously does a much cleaner job on the JPEG, and will on RAW images as well when that profile arrives."_









Canon RF 14-35mm F4L IS USM Review - DustinAbbott.net


Photographer Dustin Abbott shares a thorough review of the Canon RF 14-35mm F4L IS USM wide angle zoom for Canon EOS R mirrorless.



dustinabbott.net





I've seen so many reviews and forum threads where people have justifiably complained about the lack of lens correction profiles in their favourite post-processing software package, only to be berated by some clueless know-it-all who claims they should just make their own lens profiles and it just took them five minutes to make one. They're missing the fact that the distortion is non-linear, and it wouldn't take Adobe one year to come up with a lens profile for the RF 50mm f/1.8 (which has much lower distortion than an UWA lens) if it was that easy!


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## koenkooi (Nov 11, 2021)

LogicExtremist said:


> [..] I've seen so many reviews and forum threads where people have justifiably complained about the lack of lens correction profiles in their favourite post-processing software package, only to be berated by some clueless know-it-all who claims they should just make their own lens profiles and it just took them five minutes to make one. They're missing the fact that the distortion is non-linear, and it wouldn't take Adobe one year to come up with a lens profile for the RF 50mm f/1.8 (which has much lower distortion than an UWA lens) if it was that easy!


You can make non-linear lens profiles your self, that's the whole point of using the pattern. I also don't believe you can conclude that it took Adobe a year because it's hard, it took a year because that's how Adobe prioritized it, regardless of difficulty.


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## LogicExtremist (Nov 11, 2021)

For anyone who may be unfamiliar with what mustache distortion is, I found a good description here:






Lens Distorsions: Barrel, Pincushion & Mustache Distortion - Digital Photography Live







digitalphotographylive.com













_"Mustache Distortion contains both barrel and pincushion. At the centre of an image a barrel distortion appears and gradually turns in a pincushion shape at the edge of the same image. Probably the worst kind of lens distortion. Both the barrel and pincushion distortions are quadratic. This means that their distortions are proportional to the square of their distance from the centre. But in mustache distortion in the centre it is quadratic due to the barrel being the dominant distortion, but at the edges it becomes quartic (to the power of 4) as both barrel and pincushion distortions are visible."_

The B&H website also explains this quite well:

_"Mustache distortion, which is most commonly found in less expensive wide-angle lenses, causes straight lines to curve both inward and outward as they crisscross the horizontal and vertical planes of the photograph. While barrel and pincushion distortions, which are also known as “radial distortions,” can usually be corrected post-capture in Photoshop, Lightroom, or other photo-editing applications, mustache distortions are more difficult to correct post-capture."_









FAQ: Wide-Angle Lenses


This is an FAQ post about wide-angle lenses.




www.bhphotovideo.com





An accurate lens corection profile made specifically for the lens can fix this kind of distortion.


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## LogicExtremist (Nov 11, 2021)

koenkooi said:


> You can make non-linear lens profiles your self, that's the whole point of using the pattern. I also don't believe you can conclude that it took Adobe a year because it's hard, it took a year because that's how Adobe prioritized it, regardless of difficulty.


I'm sure that Adobe aren't just doing what customers can do in a few minutes, there's no logical reason to assume that. To assume that they either use the same tool and do it the same way as a customer, and not any other way, would be an example of the logical fallacy of false dichotomy, because it's totally possible (and most likely) that they use something more precise, which takes far longer to produce a more accurate lens profile. 

I'd say that with a leading software company's product, used by many professionals worldwide with extremely high standards, that company would put considerable effort to get things the best they can. They wouldn't keep world-class pro photogs needlessly waiting for lens profiles if the job could be completed by a junior staff member in an afternoon. Maybe the tool they provide for customers is so they can get a 'close-enough' profile for their needs, for people who think that is 'good enough', to tide customers over until the company develops proper lens profiles, could that be the case?

Even if the task took a whole afternoon, I'm sure Adobe could spare a few hours of an employee's time over a six month period to get that done. Something tells me there's probably much more involved... 

I'm not implying that it takes 12 months to complete the task of creating a lens profile for a lens with only mild distortion such as the RF 50mm f/1.8, that would be absurd. What I'm saying is that it doesn't take 5 minutes!


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## Johnw (Apr 12, 2022)

Rivermist said:


> I would also suggest along the same lines that this RF 16mm is a worthy addition to the 24-240mm all-purpose lens.



I just got this lens and I like it for what it is. I find this lens to be better than the 24-240 at least considering the comparable wide ends. The 24-240 has so much distortion optically at 24 that it doesn't even fully illuminate a FF sensor. This lens is better than that, but the optical distortion is still pretty bad before correction. Still for $300, I like this lens for what it is, basically a cheap option to play around with UWA shots, or for when you want to get at least a decent image with an ultra compact form factor. I wasn't expect pristine rendering from a lens at this price point. My choice UWA lens that I really want is the Sigma 12-24 which actually has less distortion at 12 than this lens has at 16, but at more than 5x the price, that shouldn't come as much of a surprise. Similarly the 11-24 or the forthcoming RF 10-24 would obviously blow this lens away in terms of quality, the Samyang 14 RF prime does as well for a cheaper price point.


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## neuroanatomist (Apr 12, 2022)

Johnw said:


> The 24-240 has so much distortion optically at 24 that it doesn't even fully illuminate a FF sensor.


I don’t believe that’s true. At the wide end of the zoom range, mechanical vignetting means the lens cannot cover the entire FF image circle, _but_ the wide end is actually wider than 24mm.

The 14-35/4L is similar. Strong barrel distortion and mechanical vignetting at the wide end, but that wide end is actually ~13mm. Canon’s correction of the distortion results in a 14mm FoV at the wide end. DxO PhotoLab’s correction of the distortion results in a 13.5mm FoV, a nice bonus.


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## Johnw (Apr 13, 2022)

neuroanatomist said:


> I don’t believe that’s true. At the wide end of the zoom range, mechanical vignetting means the lens cannot cover the entire FF image circle, _but_ the wide end is actually wider than 24mm.



That may indeed be the case. My main point was just that the 24-240 has more distortion at 24 than this lens does at 16, though that's not really surprising considering a 10x zoom is going to have some hard design compromises whereas its much easier in a prime to optimize the optics to do at least a halfway decent job at a fixed focal length.



neuroanatomist said:


> The 14-35/4L is similar. Strong barrel distortion and mechanical vignetting at the wide end, but that wide end is actually ~13mm. Canon’s correction of the distortion results in a 14mm FoV at the wide end. DxO PhotoLab’s correction of the distortion results in a 13.5mm FoV, a nice bonus.



Another reason I don't like the 14-35 for UWA applications. It's clearly better suited to the long end but most people looking for a UWA lens don't care as much about 35. Mediocre performance can be forgiven in a cheap lens like this 16 given it's price, but if I were to spend as much on the 14-35 as it costs for UWA I would want better rendering at the lower end.


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## neuroanatomist (Apr 13, 2022)

Johnw said:


> Another reason I don't like the 14-35 for UWA applications. It's clearly better suited to the long end but most people looking for a UWA lens don't care as much about 35. Mediocre performance can be forgiven in a cheap lens like this 16 given it's price, but if I were to spend as much on the 14-35 as it costs for UWA I would want better rendering at the lower end.


Have you tried it? I thought the same thing, before I did. I found that at 14mm, the heavily digitally corrected corners of the 14-35/4 were not significantly different from the lightly and mostly optically corrected corners of the far more expensive 11-24/4 (and the latter wasn’t at the end of its range).






RF 14-35mm f/4L IS – Distortion Correction Testing


Mirrorless cameras lack an optical viewfinder, so looking through the lens is always an electronic process. This fact enables lens manufacturers to include consideration of digital optical corrections in their lens designs and make trade-offs accordingly – more optical aberrations can be...




www.canonrumors.com


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## Johnw (Apr 13, 2022)

neuroanatomist said:


> Have you tried it? I thought the same thing, before I did. I found that at 14mm, the heavily digitally corrected corners of the 14-35/4 were not significantly different from the lightly and mostly optically corrected corners of the far more expensive 11-24/4 (and the latter wasn’t at the end of its range).



That's great if the digital correction really is that good. And I admit I have not used that lens personally. Astro is usually my main use case for UWA and my previous experience with lenses that require heavy digital correction in the corners is that they generally turn star fields into mush there. The 10-24 is also on my long term list already and I can't see myself purchasing more than one UWA zoom from Canon. For roughly the same price as the 14-35 the Sigma 12-24 seems like a better value to me for now. Weight is really the only downside I see on the Sigma and most UWA shooting I use a tripod for anyway. I've also owned the Sigma 14 1.8 and 14-24 2.8 in the past and found them both superb so I've been wanting to try that other Sigma as well until Canon releases something better (likely the 10-24).


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## neuroanatomist (Apr 13, 2022)

Johnw said:


> That's great if the digital correction really is that good. And I admit I have not used that lens personally. Astro is usually my main use case for UWA and my previous experience with lenses that require heavy digital correction in the corners is that they generally turn star fields into mush there. The 10-24 is also on my long term list already and I can't see myself purchasing more than one UWA zoom from Canon. For roughly the same price as the 14-35 the Sigma 12-24 seems like a better value to me for now. Weight is really the only downside I see on the Sigma and most UWA shooting I use a tripod for anyway. I've also owned the Sigma 14 1.8 and 14-24 2.8 in the past and found them both superb so I've been wanting to try that other Sigma as well until Canon releases something better (likely the 10-24).


It surprised me. I don't shoot much astro, have a Samyang/Rokinon 14/2.8 that i have used for that. I doubt I'd buy an RF 10-24, there's a significant advantage in adapting the EF 11-24 with the drop-in filter (granted, not for astro).


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## Johnw (Apr 13, 2022)

Filters are definitely relevant for astro. I've imaged the sun with a 20 stop ND in front of the EF-RF adapter variable ND. 

Generally though filters are more relevant for astro at telephoto lengths than UWA. Still I felt the same as you did on the 11-24 about adapting the Sigmas partly for that reason.


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## tron (Apr 13, 2022)

mccasi said:


> I have the lens too and I’m quite happy for my use cases.
> 
> 
> For selfie I don’t care about corner sharpness, but all other aberrations are perfectly controlled.
> ...


Where do you base that? I strongly doubt it! Not only from my 16-35 4L IS experience in landscape and astro but also from lenstip,com full review. Sorry but I do not accept your statement. You can like the RF16 all you want or you can pursuade yourself - I do not care - but what you say about 16-35 does not hold.


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