# What is the maximum aperture at 400mm on the Canon RF 100-500mm f/4.5-7.1L IS USM?



## Canon Rumors Guy (Jul 14, 2020)

> A question that I personally wanted to be answered has been answered at The-Digital-Picture with the help of Canon USA.
> The answer is actually quite interesting.
> *What is the Canon RF 100-500mm F4.5-7.1 L IS USM Lens’s maximum aperture opening at 400mm?*
> Answer 1: When the camera is set to 1/3-stop increments, the maximum 400mm aperture is f/6.3.
> ...



Continue reading...


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## SecureGSM (Jul 14, 2020)

Yeah.. as in camera displays / reports the aperture being f/5.6 as a rounded number while in reality it would be at f/6.3 Right?


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## sleepylamp (Jul 14, 2020)

SecureGSM said:


> Yeah.. as in camera displays / reports the aperture being f/5.6 as a rounded number while in reality it would be at f/6.3 Right?


Feels like that is the case. Someone will test and calculate the T stop, which will be a better indicator.


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## juststeve (Jul 14, 2020)

In reality, it likely means real, physical aperture is something like F6 or 6.1. When in third top mode the nearest number to round to is 6.3. In half stop mode, it is 5.6.


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## SecureGSM (Jul 14, 2020)

sleepylamp said:


> Feels like that is the case. Someone will test and calculate the T stop, which will be a better indicator.


A bit like wide end forced distortion correction on the RF 24-105 STM. You won’t know unless you are really looked for it


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## Sharlin (Jul 14, 2020)

SecureGSM said:


> Yeah.. as in camera displays / reports the aperture being f/5.6 as a rounded number while in reality it would be at f/6.3 Right?



They're both rounded, obviously. The apparent aperture size varies continuously and not in any sort of increments.


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## SecureGSM (Jul 14, 2020)

Sharlin said:


> They're both rounded, obviously. The apparent aperture size varies continuously and not in any sort of increments.


Yup, the Next half stop after f5.6 is f/6.7. Sooo... f/6.0 or f/6.1 could be the number that being rounded down to f/5.6 going in half stops and rounded up to f/6.3 if going in 1/3 of a stop. With f/6.1 being the likely real number. Not bad though. Not bad at all.


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## Steevo (Jul 14, 2020)

Didn’t Gordon Laing do a video with this lens? It was 5.6 at something like 360mm? I’d imagine it isn’t a great loss in reach with that aperture considering you now get an extra 100mm on the long end. It seems a relatively small compromise to get the RF benefits too.


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## CJudge (Jul 14, 2020)

Is Canon Rumours Guy being sarcastic with that last bit about changing settings? It’s hard to tell with text.

Because surely, when it comes to max aperture on variable aperture zooms, the number reflected in the metadata is always a rounded figure. The aperture isn’t mechanically clicking into different positions during the zoom... it’s simply the calculated value based on the entrance pupil in relation to the changing focal length. Right?


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## bbasiaga (Jul 14, 2020)

The thing to remember is the 100-400 isn't exactly 5.6 at 400mm either. IN fact I think that lens isn't actually 400mm, but I can't recall which variation. Might have ended at like 380mm in actuality. All camera lenses are approximate stops near the ends of their ranges. This is why, as I understand it - and I may not have all the right understanding - cinema lenses are listed in T stops instead. You can take two lenses and know you are getting the same transmittence/light flux on both of them.


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## SecureGSM (Jul 14, 2020)

bbasiaga said:


> The thing to remember is the 100-400 isn't exactly 5.6 at 400mm either. IN fact I think that lens isn't actually 400mm, but I can't recall which variation. Might have ended at like 380mm in actuality. All camera lenses are approximate stops near the ends of their ranges. This is why, as I understand it - and I may not have all the right understanding - cinema lenses are listed in T stops instead. You can take two lenses and know you are getting the same transmittence/light flux on both of them.


Around 386mm on top of my head..


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## SecureGSM (Jul 14, 2020)

bbasiaga said:


> The thing to remember is the 100-400 isn't exactly 5.6 at 400mm either. IN fact I think that lens isn't actually 400mm, but I can't recall which variation. Might have ended at like 380mm in actuality. All camera lenses are approximate stops near the ends of their ranges. This is why, as I understand it - and I may not have all the right understanding - cinema lenses are listed in T stops instead. You can take two lenses and know you are getting the same transmittence/light flux on both of them.


What it means to me though is that the lens is not a f/6.6 rounded down to f/6.3 but f6.1 rounded up to f/6.3 when going in 1/3 of a stop. Good.


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## AlanF (Jul 14, 2020)

SecureGSM said:


> Around 386mm on top of my head..


But what on your camera?


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## AlanF (Jul 14, 2020)

Steevo said:


> Didn’t Gordon Laing do a video with this lens? It was 5.6 at something like 360mm? I’d imagine it isn’t a great loss in reach with that aperture considering you now get an extra 100mm on the long end. It seems a relatively small compromise to get the RF benefits too.


Here it is again as it is most pertinent.


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## Billybob (Jul 14, 2020)

What it means to me is that the 100-500 will be slightly darker than the 100-400 at 400mm. With the high DR of modern cameras, this is totally irrelevant to me. I shoot RAW, and it's rare that I don't tweak good shots in post. Although I wish that Canon had been more upfront that the light transmission is slightly lower at 400mm, for me it is a reasonable tradeoff if I'm getting equal or better IQ and an extra 100mm of reach in roughly the same-size package. I hear some grumble about not getting 600mm and 6.3 at the long end, but I don't want the extra weight and bulk that's required for those specs when I'm traveling or when I want to do close-up photography. What the extra $700 buys you over the $2000 super-tele-zooms is flexibility (100mm versus 150-200 at the short end), compact size and weight (1.5-2.5lbs saving), closer focusing, and hopefully better IQ throughout the range. For me, these are great benefits.


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## SecureGSM (Jul 14, 2020)

AlanF said:


> But what on your camera?


EF 100-400 II L if that’s what you were asking?


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## Skyscraperfan (Jul 14, 2020)

It would be nice if Canon finally released the manuals of the R5 and R6. Do they expect people to order those camaras without having read the manual? Then we would know how easy it is to change from 1/2 to 1/3 increments and back.


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## JustUs7 (Jul 14, 2020)

Skyscraperfan said:


> It would be nice if Canon finally released the manuals of the R5 and R6. Do they expect people to order those camaras without having read the manual? Then we would know how easy it is to change from 1/2 to 1/3 increments and back.



My sarcasm detector is buzzing a little. Manuals would be nice, sure, but for that reason?


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## bbasiaga (Jul 14, 2020)

Skyscraperfan said:


> It would be nice if Canon finally released the manuals of the R5 and R6. Do they expect people to order those camaras without having read the manual? Then we would know how easy it is to change from 1/2 to 1/3 increments and back.


I mean, i feel like the acronym RTFM was created precisely because people don't...well...read the manual. LOL


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## Bert63 (Jul 14, 2020)

Never mind all the numbers silliness, does it take good 'pitchers'?

Dem pitchers is all I cares about ya knows.


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## koenkooi (Jul 14, 2020)

Bert63 said:


> Never mind all the numbers silliness, does it take good 'pitchers'?
> 
> Dem pitchers is all I cares about ya knows.



Do yer pitchers have enough megapickles?


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## JustUs7 (Jul 14, 2020)

koenkooi said:


> Do yer pitchers have enough megapickles?


Is there such a thing?


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## dtaylor (Jul 14, 2020)

> Hopefully, Canon makes it easy to switch between 1/3 and 1/2 increments when using the Canon RF 100-500mm f/4.5-7.1L IS USM with your EOS R5 & EOS R6.



Queue Tony and Chelsea complaining about this very thing in their next video.


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## Bert63 (Jul 14, 2020)

koenkooi said:


> Do yer pitchers have enough megapickles?



Dey will as soon as da dang R5 shows up on muh doorsteps.


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## Bert63 (Jul 14, 2020)

dtaylor said:


> Queue Tony and Chelsea complaining about this very thing in their next video.




No. Please. Not them. Anything but them.


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## AlanF (Jul 14, 2020)

I am trying to make sense of why there is a difference when using 1/3rd rather half stops. The first is to note that f/4 to f/7.1 can be divided nicely into five 1/3rd stops: 7.1 - 6.3 - 5.6 - 5.0 - 4.5, with values we are all used to seeing. The progression in 0.5 stops doesn't fit, e.g. 7.1 - 6.0 - 5.0 - 4.2 is the progressive increase in 1/2s and doesn't use f-numbers that are usually seen. Or, 4.5 - 5.3 - 6.3 - 7.4 is a similar bad fit. A plot of f-number against focal length based on when the f-number starts on the Cameralabs chart gives a nice straight line. All this suggests to me that the 1/3rd stops are more realistic, and the 1/2 stops are just numbers spewed out by Canon to be ones we are used to seeing, like 5.6, and aren't real.


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## Act444 (Jul 14, 2020)

So basically, beyond 250mm you’re giving up 1/3 stop compared to the 100-400. F5.6 at 300mm (vs f5) and f6.3 at 400mm (vs 5.6). But in exchange, you get to reach 500mm. Ok. About what I expected.

I’d like to see if there’ll be an 80-400 4 or 4.5 to 5.6 type lens in this class on the horizon for the RF system. There is space for one, methinks...


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## Sharlin (Jul 14, 2020)

AlanF said:


> All this suggests to me that the 1/3rd stops are more realistic, and the 1/2 stops are just numbers spewed out by Canon to be ones we are used to seeing, like 5.6, and aren't real.



Both the 1/3 and the 1/2 stop scale are approximations. The lens is almost certainly physically not exactly 100–500mm f/4.5–7.1, those are just familiar figures that the actual physical values are rounded to. At least at some focal lengths the 1/2 scale may actually be a better approximation, but 1/3 happens to be the one that most people use and is, of course, the more fine-grained of the two.


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## AlanF (Jul 14, 2020)

Sharlin said:


> Both the 1/3 and the 1/2 stop scale are approximations. The lens is almost certainly physically not exactly 100–500mm f/4.5–7.1, those are just familiar figures that the actual physical values are rounded to. At least at some focal lengths the 1/2 scale may actually be a better approximation, but 1/3 happens to be the one that most people use and is, of course, the more fine-grained of the two.


Where would a coarser-grained approximation be better for some focal lengths? A genuine question, I realise that a clock that is stopped is absolutely correct twice a day but one that is 1 minute fast never is never right.


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## BillB (Jul 14, 2020)

Skyscraperfan said:


> It would be nice if Canon finally released the manuals of the R5 and R6. Do they expect people to order those camaras without having read the manual? Then we would know how easy it is to change from 1/2 to 1/3 increments and back.


If it works the_ same way on the R5 and the R6 as on current Canon cameras it won‘t be hard to change From 1/2 to 1/3 increments if you read the manual._


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## BillB (Jul 14, 2020)

AlanF said:


> Where would a coarser-grained approximation be better for some focal lengths? A genuine question, I realise that a clock that is stopped is absolutely correct twice a day but one that is 1 minute fast never is never right.


The difference between 1/3 stop and 1/2 stop is 1/6 stop, which isn‘t all that much.


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## Sharlin (Jul 14, 2020)

AlanF said:


> Where would a coarser-grained approximation be better for some focal lengths? A genuine question, I realise that a clock that is stopped is absolutely correct twice a day but one that is 1 minute fast never is never right.


Given that the apparent aperture size varies continuously and smoothly as a function of the focal length, there’s necessarily a point where, say, f/6.7 (the half step between 5.6 and 8) is a better approximation of the real aperture ratio than either f/6.3 or f/7.1. But of course differences of just 1/6 stops are mostly academic anyway.


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## subtraho (Jul 14, 2020)

This whole discussion makes me wish cameras let you adjust their internal rounding in higher-granularity increments like 1/10 (or finer) of a stop, we'd probably learn a lot about our lenses if they did. Likely not practical for real-world usage, however - plus it would probably expose quite a few creative marketing shenanigans - so it'll never happen. I do have an older Pentax 55-300mm f/4-5.8 that was a bit of a head-scratcher at the time, but in retrospect was just using a higher-granularity f/stop scale.


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## AlanF (Jul 14, 2020)

BillB said:


> The difference between 1/3 stop and 1/2 stop is 1/6 stop, which isn‘t all that much.


The difference between reported values of f/5.6 and f/6.3 at 400mm is a 1/3 stop so how does a 1/6 stop account for that?


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## dcm (Jul 14, 2020)

AlanF said:


> Here it is again as it is most pertinent.
> View attachment 191338



Something similar happens with the 100-400L on my 1DXII. If you set the 1DX II exposure level increment to half stops with the 100-400L II, the f/4.5 (not a half stop) range extends from 100-312mm and jumps to f/5.6 for 312-400mm. In this scenario f/5 never occurs. It's somewhat interesting that it never chooses the half stop at f/4.8, even when you manually control the aperture.


Changing the exposure level increment simply changes the values that can be selected and gives you less granularity in exposure choices.


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## brad-man (Jul 15, 2020)

Bert63 said:


> Never mind all the numbers silliness, does it take good 'pitchers'?
> 
> Dem pitchers is all I cares about ya knows.


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## BillB (Jul 15, 2020)

AlanF said:


> The difference between reported values of f/5.6 and f/6.3 at 400mm is a 1/3 stop so how does a 1/6 stop account for that?


If the lens is reporting f6.3 using 1/3 stop increments the actual measurement has to be closer to f6.3 than to f5.6. If same lens is reporting f5.6 using 1/2 stop increments, the actual measurement has to be closer to f5.6 than to f6.7, or whatever the half stop value is. So, for the lens to read F5.6 using half stop increments and read f6.3 using 1/3 stop increments, the actual measurement has to be between (half the difference between f5.6 and f6.3) and (half the difference between f5.6 and f6.7). Dividing a stop into twelfths the actual difference has to between (1/2 (4/12)) stops and (1/2( 6/12)) stops or between 2/12 and 3/12 stops above f5.6. So, the max discrepancy resulting from the lens reading f5.6 with half stop increments and reading f6.3 with third stop increments would be a a twelfth of a stop. (Not a sixth of a stop I said previously.)


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## juststeve (Jul 15, 2020)

For those who were sleeping through third grade arithmetic, 1/2 = 3/6. 1/3 = 2/6. 3/6 - 2/6 = 1/6.

And for what it is worth, memory is Canon calculates f stops in camera in tenths, since early EF days. Those wishing for the info in print may want to check specs for Cinema EOS and EF lenses.

So what you are seeing is simply the rounding off of numbers to the nearest whatever. The diameter of the aperture at any given focal length is going to be a constant, but one determined by a bunch of variables. After-all, there are going to be anywhere from six to eight groups of elements moving around in that lens at it is zoomed. The actual physical diameter of the aperture may be changing as well as the lens is zoomed. Its position within the lens relative to other groups of elements almost certainly is changing.

A lot of things moving and a grooving in that lens.
.


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## LSXPhotog (Jul 15, 2020)

If any of you are seriously considering buying this lens and switching your cameras on 1/2-stop increments just so your camera displays 5.6 at 400mm...you should reconsider the importance of that arbitrary difference. LOL

Great to hear the lens isn't 7.1 at 400mm, that's for sure. I really like this lens a lot but not that price tag! If I sold my 70-200 and 100-400 it STILL wouldn't fund the purchase!


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## Eclipsed (Jul 15, 2020)

Do the “rounding errors“ EVER deliver more than promised?


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## Antono Refa (Jul 15, 2020)

juststeve said:


> And for what it is worth, memory is Canon calculates f stops in camera in tenths, since early EF days. Those wishing for the info in print may want to check specs for Cinema EOS and EF lenses.



Why would Canon calculate f stops in tenths of a stop? Did Canon ever make stills cameras that allowed changing the aperture in anything but half or full stops?


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## SteveC (Jul 15, 2020)

Antono Refa said:


> Why would Canon calculate f stops in tenths of a stop? Did Canon ever make stills cameras that allowed changing the aperture in anything but half or full stops?



I don't know what he meant by this. But I am not going to *assume* that he meant tenths of a stop when he only said tenths.


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## SecureGSM (Jul 15, 2020)

AlanF said:


> I am trying to make sense of why there is a difference when using 1/3rd rather half stops. The first is to note that f/4 to f/7.1 can be divided nicely into five 1/3rd stops: 7.1 - 6.3 - 5.6 - 5.0 - 4.5, with values we are all used to seeing. The progression in 0.5 stops doesn't fit, e.g. 7.1 - 6.0 - 5.0 - 4.2 is the progressive increase in 1/2s and doesn't use f-numbers that are usually seen. Or, 4.5 - 5.3 - 6.3 - 7.4 is a similar bad fit. A plot of f-number against focal length based on when the f-number starts on the Cameralabs chart gives a nice straight line. All this suggests to me that the 1/3rd stops are more realistic, and the 1/2 stops are just numbers spewed out by Canon to be ones we are used to seeing, like 5.6, and aren't real.
> 
> View attachment 191347


Yes, it’s likely f/6.1 (T6.1) in reality rounded down to f/5.6 in 1/2 stop steps or up to f/6.3 in 1/3 stop steps.


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## YeTi73 (Jul 15, 2020)

f7.1 is not fast enough.
For wild life photograph you'll have to boost ISO to 6400, even in "good light condition". not a good idea to mess with ISO over 3200.
I use D5, yes I was a traitor :-/ (finger cross for R5)
I hope Canon can make a lenses faster while still within budget, like Sony 200-600 f5.6-6.3, which at 600mm you got f6.3. is that price unreachable? Not at all.
Mainly, its for marketing consideration, that's why I will keep my 100-400 mk II. Both are excellent lenses I believe.
Another question is, can R5 replace or challenge their flagship, like 1dx III? Not a chance.
Manual + auto ISO(my favorite shooting mode), they just won't let you have that.
Still, for marketing reason.


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## Joules (Jul 15, 2020)

I agree that all of this is silly. It's splitting hairs. But, doing it in such an odd way. 

So, what is the actual focal length of the EF 100-400 L II when set to 400 mm? I know somebody measured it at some point. Can't remember where that was, don't have time to find it. The point is, we're discussing the inaccuracies of the stated f/ value, while ignoring the inaccuracies in the stated focal length. If you want to split hairs, do it right and compare apples to apples. Really, without shooting side by side pictures taken at the same FoV from both lenses and comparing the actual image qualities rather than the numbers, I can't see any information of value coming out of this discussion.


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## CJudge (Jul 15, 2020)

YeTi73 said:


> Another question is, can R5 replace or challenge their flagship, like 1dx III? Not a chance.
> Manual + auto ISO(my favorite shooting mode), they just won't let you have that.
> Still, for marketing reason.



What are you talking about? Every Canon I’ve ever owned, including my EOS R, has let me shoot Manual + auto ISO.


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## CJudge (Jul 15, 2020)

subtraho said:


> This whole discussion makes me wish cameras let you adjust their internal rounding in higher-granularity increments like 1/10 (or finer) of a stop, we'd probably learn a lot about our lenses if they did. Likely not practical for real-world usage, however - plus it would probably expose quite a few creative marketing shenanigans - so it'll never happen.



I know that in my EOS R, in movie mode, it’s possible to set the aperture control to 1/8th stop increments. Not available in stills mode, but as you said it would be impractical.


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## YeTi73 (Jul 15, 2020)

CJudge said:


> What are you talking about? Every Canon I’ve ever owned, including my EOS R, has let me shoot Manual + auto ISO.


Sorry, my bad. To make it clear, what I mean is: "Manual mode (you decide f number as well as shutter speed) and set ISO to Auto", then let the camera to decide the proper exposure. Try that one, I don't think any non-flagship camera has that.


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## Joules (Jul 15, 2020)

YeTi73 said:


> Sorry, my bad. To make it clear, what I mean is: "Manual mode (you decide f number as well as shutter speed) and set ISO to Auto", then let the camera to decide the proper exposure. Try that one, I don't think any non-flagship camera has that.


And I think you are wrong.

80D, Mode dial set to M so that I can set the shutter speed and f-number I want and ISO set to Auto (with the option to restrict the range via menu) works perfectly fine.


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## Antono Refa (Jul 15, 2020)

SteveC said:


> I don't know what he meant by this. But I am not going to *assume* that he meant tenths of a stop when he only said tenths.



OK, then tenths of what? If he means one digit after the decimal point, I think that's practically the industry standard. I don't recall ever seeing f & t stops given with two or more digits after the decimal point, outside of photography 101 explanations of the subject.


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## navastronia (Jul 15, 2020)

YeTi73 said:


> Sorry, my bad. To make it clear, what I mean is: "Manual mode (you decide f number as well as shutter speed) and set ISO to Auto", then let the camera to decide the proper exposure. Try that one, I don't think any non-flagship camera has that.



They do. My $1099 EOS RP does it.


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## Rbus (Jul 15, 2020)

Skyscraperfan said:


> It would be nice if Canon finally released the manuals of the R5 and R6. Do they expect people to order those cameras without having read the manual? Then we would know how easy it is to change from 1/2 to 1/3 increments and back.



If it is like all the other Canon Camera's I have owned then it will be in the menu's and easy to to change, although I cannot understand why you would want to after your initial setup.


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## Steve Balcombe (Jul 15, 2020)

juststeve said:


> In reality, it likely means real, physical aperture is something like F6 or 6.1. When in third top mode the nearest number to round to is 6.3. In half stop mode, it is 5.6.


Exactly right - so maybe a 1/4 stop slower than the 100-400 at that specific focal length. And the comparison chart which somebody put together shows that overall there is very little difference between the EF 100-400 and the RF 100-500 through the range - except for 401-500 mm of course. The whole thing is a storm in a teacup.


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## Deleted member 381342 (Jul 15, 2020)

YeTi73 said:


> f7.1 is not fast enough.
> For wild life photograph you'll have to boost ISO to 6400, even in "good light condition". not a good idea to mess with ISO over 3200.
> I use D5, yes I was a traitor :-/ (finger cross for R5)
> I hope Canon can make a lenses faster while still within budget, like Sony 200-600 f5.6-6.3, which at 600mm you got f6.3. is that price unreachable? Not at all.
> ...



If f/7.1 isn’t fast enough I fail to see why 1/3rd of a stop will make a difference. ISO 6400 is unacceptable but ISO 5000 is? Not forgetting there will be a large IQ difference between a Canon L lens and a consumer 200-600mm.


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## Deleted member 381342 (Jul 15, 2020)

Joules said:


> I agree that all of this is silly. It's splitting hairs. But, doing it in such an odd way.
> 
> So, what is the actual focal length of the EF 100-400 L II when set to 400 mm? I know somebody measured it at some point. Can't remember where that was, don't have time to find it. The point is, we're discussing the inaccuracies of the stated f/ value, while ignoring the inaccuracies in the stated focal length. If you want to split hairs, do it right and compare apples to apples. Really, without shooting side by side pictures taken at the same FoV from both lenses and comparing the actual image qualities rather than the numbers, I can't see any information of value coming out of this discussion.



About 380mm is what I recall.


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## koenkooi (Jul 15, 2020)

Codebunny said:


> About 380mm is what I recall.



IIRC Alan_F measured it to be slightly below 200mm at MFD, so it depends on how far away you're focussing.


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## tron (Jul 15, 2020)

OK maybe f/7.1 is something in between. Not "fast enough" but not "too slow" either.

Slightly off topic but the f/5.6 of Nikon 500mm 5.6E PF is better though 

BUT truth be told: if I ever upgraded my R to R5 I would be curious about 100-500... (and it has that 100 to 499mm range too...)


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## Richard Anthony (Jul 15, 2020)

I have just ordered this , so its been interesting reading all the comments .


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## CJudge (Jul 15, 2020)

YeTi73 said:


> Sorry, my bad. To make it clear, what I mean is: "Manual mode (you decide f number as well as shutter speed) and set ISO to Auto", then let the camera to decide the proper exposure. Try that one, I don't think any non-flagship camera has that.



That's what I'm talking about too. Unless I'm still misunderstanding you...

No matter what shooting mode you are in, when you go into the ISO selection, you can always pick "auto". I often use that when shooting events, because I want to control the other two factors, but the changing light conditions make auto ISO helpful for staying in the correct exposure ball-park.


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## CJudge (Jul 15, 2020)

Codebunny said:


> If f/7.1 isn’t fast enough I fail to see why 1/3rd of a stop will make a difference. ISO 6400 is unacceptable but ISO 5000 is? Not forgetting there will be a large IQ difference between a Canon L lens and a consumer 200-600mm.



I've seen people on other sites make similar complaints about the upcoming 85mm f/2. Claiming that f/1.8 is a wonderful portrait option, but f/2 is "unusable" for portraits. I swear, some people get way too hung up on 1/3rd of a stop.

In practical use, I could barely see a DOF difference between my old EF 24-70 f/2.8L ii and the RF 28-70 f/2. And that's coming from someone who happily bought the RF lens after testing! Rendering will take precedence over max aperture any day of the week. Which is why the 100mm f/2.8L remains my favourite lens. (It just so happens that the RF 28-70 ticks both boxes)


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## scyrene (Jul 15, 2020)

Tbh this is something I should have known, but I guess it's so long since I used a variable aperture zoom, and back then I didn't know much about photography. It makes sense it should work this way and is a neat insight to how zoom lenses work, but the whole discussion makes me feel the endless back and forth pre-release about whether this was f/5.6 or f/6.3 at 400mm is again a matter of meaningless nitpicking. If the differences can be accounted for by rounding errors, then they are surely of no practical relevance to real world use? I get that a lot of people feel less is worse, but I doubt anyone could tell even from their own shots whether two photographs of the same focal length were at f/5.6 versus f/6.3, let along what T stop that actually represents.


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## Deleted member 381342 (Jul 15, 2020)

CJudge said:


> I've seen people on other sites make similar complaints about the upcoming 85mm f/2. Claiming that f/1.8 is a wonderful portrait option, but f/2 is "unusable" for portraits. I swear, some people get way too hung up on 1/3rd of a stop.
> 
> In practical use, I could barely see a DOF difference between my old EF 24-70 f/2.8L ii and the RF 28-70 f/2. And that's coming from someone who happily bought the RF lens after testing! Rendering will take precedence over max aperture any day of the week. Which is why the 100mm f/2.8L remains my favourite lens. (It just so happens that the RF 28-70 ticks both boxes)



I have a 85mm f/1.8 S on my Nikon.... I honest to goodness can't tell between f/1.8 and f/2.0 when I take a picture. I have to go to f/4 or f/5.6 before there is a real big change to the DOF. And all times my shutter speed is way up there. The Canon 85mm f/2.0 is probably not going to compete with the Nikon on IQ, its not a L series. But it will be a absolutely cracking lens that will take lovely images with 'dreamy' OOF areas. I think there is some old thinking here about having to stop down lenses, I definitely hear it on the Nikon side against the 1.8 S lenses where people still think you need to stop it down so they want a f/1.2 lens so it is sharp when stopped down... these new lenses from Nikon and Canon are sharp wide open and if anything you have to add in defects in post. I often at in a bit of vignetting as the images are a little too perfect.


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## Billybob (Jul 15, 2020)

YeTi73 said:


> f7.1 is not fast enough.
> For wild life photograph you'll have to boost ISO to 6400, even in "good light condition". not a good idea to mess with ISO over 3200.
> I use D5, yes I was a traitor :-/ (finger cross for R5)
> I hope Canon can make a lenses faster while still within budget, like Sony 200-600 f5.6-6.3, which at 600mm you got f6.3. is that price unreachable? Not at all.
> ...


I, respectfully, disagree. Your statement about f/7.1 is widely exaggerated. I went back and took a look at some bird shots taken at f/7.1 ISO320. The shutter was 1/1600, but I could have easily raised it to 1/2000 or 1/2500 while keeping ISO at 1600 or lower. I also found some D5 BIF shots taken at f/8, ISO800 and 1/2500 These shots were taken in morning sun, so definitely good light and plenty bright. If taken at twilight or later, yes I would have had to raise the ISO, but for anything but early, early morning, twilight, or extreme overcast, f/7.1-f/10 are fine.


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## arbitrage (Jul 15, 2020)

YeTi73 said:


> Sorry, my bad. To make it clear, what I mean is: "Manual mode (you decide f number as well as shutter speed) and set ISO to Auto", then let the camera to decide the proper exposure. Try that one, I don't think any non-flagship camera has that.



A lot of Canon cameras have had M + Auto ISO for a long while. At first the issue was they wouldn't let you set EC in M+AutoISO so that made the mode next to useless. However starting back at the 1DX, 7DII, 5DS/R and onwards there has been full functionality to M + AutoISO with proper EC control (which is needed in any mode other than full M). 80D had it also. I'm not sure if any Rebels have it or not. It certainly isn't just flagships and even with 1 series flagships the first to have it working properly was the 1DX.


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## arbitrage (Jul 15, 2020)

YeTi73 said:


> f7.1 is not fast enough.
> For wild life photograph you'll have to boost ISO to 6400, even in "good light condition". not a good idea to mess with ISO over 3200.
> I use D5, yes I was a traitor :-/ (finger cross for R5)
> I hope Canon can make a lenses faster while still within budget, like Sony 200-600 f5.6-6.3, which at 600mm you got f6.3. is that price unreachable? Not at all.
> ...


ISO 3200 just because you are at f/7.1?...have you every heard of the sunny 16 rule? Even at f/16 in full sun you would need to be using 1/3200s to have to use ISO 3200. You have 2 1/3 stops to work with at f/7.1 compared to the Sunny 16 rule. In full sun at 1/3200s you would be at around ISO640. Sure f/7.1 will become limiting in some very dreary conditions and will eventually force you to ISO 3200. But anything in nice golden light (why shoot in anything else??) is not going to get you anywhere near ISO 3200 even with a very fast SS and f/7.1.


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## Jack Douglas (Jul 15, 2020)

Wow, the virus really is taking its toll on (some) peoples mental health! 

Jack


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## BeenThere (Jul 15, 2020)

Jack Douglas said:


> Wow, the virus really is taking its toll on (some) peoples mental health!
> 
> Jack


Much ado about nothing.


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## koenkooi (Jul 15, 2020)

Codebunny said:


> I have a 85mm f/1.8 S on my Nikon.... I honest to goodness can't tell between f/1.8 and f/2.0 when I take a picture. I have to go to f/4 or f/5.6 before there is a real big change to the DOF. And all times my shutter speed is way up there. The Canon 85mm f/2.0 is probably not going to compete with the Nikon on IQ, its not a L series. But it will be a absolutely cracking lens that will take lovely images with 'dreamy' OOF areas. I think there is some old thinking here about having to stop down lenses, I definitely hear it on the Nikon side against the 1.8 S lenses where people still think you need to stop it down so they want a f/1.2 lens so it is sharp when stopped down... these new lenses from Nikon and Canon are sharp wide open and if anything you have to add in defects in post. I often at in a bit of vignetting as the images are a little too perfect.



On the EF85/1.8 you can see a big difference between f/1.8 and f/2.2, a lot of the abberations become too small to notice while DoF stays acceptable. I mostly use it f/2.5, so the RF f/2.0 would be an improvement


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## Deleted member 381342 (Jul 15, 2020)

koenkooi said:


> On the EF85/1.8 you can see a big difference between f/1.8 and f/2.2, a lot of the abberations become too small to notice while DoF stays acceptable. I mostly use it f/2.5, so the RF f/2.0 would be an improvement



Aye a lot of the older lenses like the 50mm f/1.8 where good at f/2.8 or even f/4. These new lenses at lease the Nikon ones are excellent at f/1.8 all the way to the edge. Now clearly those are more akin to L glass but I see no reason why RF with its new big mount won’t have f/2 being super sharp without needing stopped down. Especially if the f/1.2 lenses are any indication of what primes are like on RF.


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## 1D4 (Jul 15, 2020)

tron said:


> OK maybe f/7.1 is something in between. Not "fast enough" but not "too slow" either.
> 
> Slightly off topic but the f/5.6 of Nikon 500mm 5.6E PF is better though
> 
> BUT truth be told: if I ever upgraded my R to R5 I would be curious about 100-500... (and it has that 100 to 499mm range too...)



The Nikkor 500PF is also a specialized prime lens that costs $800 USD more and has a waiting list of about 6 months. The 100-500 is a general purpose superzoom....not slightly off-topic, but completely off-topic, just like all the people I've seen saying the RF 100-500 is a ripoff because the Nikkor 200-500 is half the price.


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## Harold Lee (Jul 15, 2020)

Actually, when you change to 1/2 stop, the maximum aperture of 24-105mm f/4-7.1 at 105mm is f/6.7.


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## AlanF (Jul 15, 2020)

arbitrage said:


> ISO 3200 just because you are at f/7.1?...have you every heard of the sunny 16 rule? Even at f/16 in full sun you would need to be using 1/3200s to have to use ISO 3200. You have 2 1/3 stops to work with at f/7.1 compared to the Sunny 16 rule. In full sun at 1/3200s you would be at around ISO640. Sure f/7.1 will become limiting in some very dreary conditions and will eventually force you to ISO 3200. But anything in nice golden light (why shoot in anything else??) is not going to get you anywhere near ISO 3200 even with a very fast SS and f/7.1.


I've routinely used f/8 (100-400mm II + 1.4xTC on a 5DSR and 400 f/4 + 2xTC on a 5DIV) for BIF like many others (including Jack on his 1DXII). There are too many comments about using these lenses from those who clearly have never used telephotos or calculated the settings for full manual exposure.


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## tron (Jul 15, 2020)

1D4 said:


> The Nikkor 500PF is also a specialized prime lens that costs $800 USD more and has a waiting list of about 6 months. The 100-500 is a general purpose superzoom....not slightly off-topic, but completely off-topic, just like all the people I've seen saying the RF 100-500 is a ripoff because the Nikkor 200-500 is half the price.


Well the underlined part of yours was off topic too since you mentioned that in a different thread and this thread is not about the price. Anyway it is nice that with 11 posts you were almost self-appointed as the thread moderator !


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## YeTi73 (Jul 15, 2020)

Billybob said:


> I, respectfully, disagree. Your statement about f/7.1 is widely exaggerated. I went back and took a look at some bird shots taken at f/7.1 ISO320. The shutter was 1/1600, but I could have easily raised it to 1/2000 or 1/2500 while keeping ISO at 1600 or lower. I also found some D5 BIF shots taken at f/8, ISO800 and 1/2500 These shots were taken in morning sun, so definitely good light and plenty bright. If taken at twilight or later, yes I would have had to raise the ISO, but for anything but early, early morning, twilight, or extreme overcast, f/7.1-f/10 are fine.


D5, f/7.1 speed 1/1600s at morning, around 8 or 9, can't remember accurately.(for wild life that's a "good light condition", normally I do not walk around in the noon so does most of the animals)...chose f/7.1 to keep both birds in focus, Manual mode, ISO automatically boost to 6400.
For online post or web use that's fine, but I do wish I could stay NO higher than ISO 3200, mainly because of the COLOR not the noise.

For M+Auto ISO, I use from EOS 1V, 5d Mark II, Mark IV...those combinations are different from flagship such as D5. That's my personal experience, but possibly I didn't study the user manual carefully, therefore I maybe use them "differently"


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## AlanF (Jul 15, 2020)

scyrene said:


> Tbh this is something I should have known, but I guess it's so long since I used a variable aperture zoom, and back then I didn't know much about photography. It makes sense it should work this way and is a neat insight to how zoom lenses work, but the whole discussion makes me feel the endless back and forth pre-release about whether this was f/5.6 or f/6.3 at 400mm is again a matter of meaningless nitpicking. If the differences can be accounted for by rounding errors, then they are surely of no practical relevance to real world use? I get that a lot of people feel less is worse, but I doubt anyone could tell even from their own shots whether two photographs of the same focal length were at f/5.6 versus f/6.3, let along what T stop that actually represents.


For those of us who are interested, it's not nitpicking but a desire to understand how our gear works and how to squeeze the best out of it. You don't have to understand much at all to get good images out of a camera or create works of art, but the technology is of great interest as well if you have a scientific bent.


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## 1D4 (Jul 15, 2020)

tron said:


> Well the underlined part of yours was off topic too since you mentioned that in a different thread. Anyway it is nice that with 11 posts you were almost self-appointed as the thread moderator !


"Off-topic" as in the 500PF is a totally different, incomparable type of lens, so it's not "slightly off topic" [your words, not mine]...the two lenses have nothing to do with one another. Way to miss the point.


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## tron (Jul 15, 2020)

1D4 said:


> "Off-topic" as in the 500PF is a totally different, incomparable type of lens, so it's not "slightly off topic" [your words, not mine]...the two lenses have nothing to do with one another. Way to miss the point.


If I recall correctly I myself mentioned the 100-499 range...
Congratulations on your friendly 12th post by the way...


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## SecureGSM (Jul 15, 2020)

Harold Lee said:


> Actually, when you change to 1/2 stop, the maximum aperture of 24-105mm f/4-7.1 at 105mm is f/6.7.


And in full stop steps it is F5.6. even Better!


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## 1D4 (Jul 15, 2020)

tron said:


> If I recall correctly I myself mentioned the 100-499 range...
> Congratulations on your friendly 12th post by the way...



1) Oh yes, because the number of posts one has on CanonRumors equates to their photography level or intelligence.
2) You said "Slightly off topic but the f/5.6 of Nikon 500mm 5.6E PF is better though". I was saying you can't compare totally different lenses that have completely different purposes. That's like me saying "but the f/4.0 of the Canon EF Telephoto 500mm F/4.0 IS II is better though". If Canon wanted to make a 100-500mm f4-5.6, they could have, but it would have been heavier, bigger, and more expensive than what they were going for. They may very well make a RF 500mm f5.6. But that is not the purpose of the RF 100-500.


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## tron (Jul 15, 2020)

1D4 said:


> 1) Oh yes, because the number of posts one has on CanonRumors equates to their photography level or intelligence.
> 2) You said "Slightly off topic but the f/5.6 of Nikon 500mm 5.6E PF is better though". I was saying you can't compare totally different lenses that have completely different purposes. That's like me saying "but the f/4.0 of the Canon EF Telephoto 500mm F/4.0 IS II is better though". If Canon wanted to make a 100-500mm f4-5.6, they could have, but it would have been heavier and more expensive than what they were going for. They may very well make a RF 500mm f5.6. But that is not the purpose of the RF 100-500.


I was putting emphasis on friendliness! It seems you were written in this forum mainly to argue with people (judging by the other thread you yourself mentioned). Every person has different criteria for their needs in wildlife and birding photography just like any other kind of photography. With this in mind I do not need to have your permission to comment on this thread. And don't put words in my mouth. Once more - since you do not seem to have read that - I myself mentioned the 100-499 range advantage of Canon's RF lens).

EDIT: And another member in this forum mentioned D5 and yet another SONY 200-600. Should they get your permission too?


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## 1D4 (Jul 15, 2020)

tron said:


> I was putting emphasis on friendliness! It seems you were written in this forum mainly to argue with people (judging by the other thread you yourself mentioned). Every person has different criteria for their needs in wildlife and birding photography just like any other kind of photography. With this in mind I do not need to have your permission to comment on this thread. And don't put words in my mouth. Once more - since you do not seem to have read that - I myself mentioned the 100-499 range advantage of Canon's RF lens).
> 
> EDIT: And another member in this forum mentioned D5 and yet another SONY 200-600. Should they get your permission too?



It's amazing you looked through my post history and concluded I mainly argue with people. You should probably look again and not cherry pick the one or two times I've DISAGREED with someone who was making an illogical statement.

AGAIN, thanks for painting me as "forum police" when that's just because you totally misinterpreted (and continue to misinterpret) what I said. I'm done talking to you.


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## scyrene (Jul 15, 2020)

AlanF said:


> For those of us who are interested, it's not nitpicking but a desire to understand how our gear works and how to squeeze the best out of it. You don't have to understand much at all to get good images out of a camera or create works of art, but the technology is of great interest as well if you have a scientific bent.



With all due respect that doesn't answer my question - if nobody can reliably tell a difference between 1/3 of a stop exposure change due to different apertures compensated by ISO or shutter speed, then how does it make a _practical difference_? I don't think 'nitpicking' is mischaracterisation of most of the discussion regarding differences between the two lenses.


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## BeenThere (Jul 15, 2020)

AlanF said:


> For those of us who are interested, it's not nitpicking but a desire to understand how our gear works and how to squeeze the best out of it. You don't have to understand much at all to get good images out of a camera or create works of art, but the technology is of great interest as well if you have a scientific bent.


I have to disagree that “You don’t have to understand much at all to...... create works of art”.


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## SteveC (Jul 15, 2020)

Antono Refa said:


> OK, then tenths of what? If he means one digit after the decimal point, I think that's practically the industry standard. I don't recall ever seeing f & t stops given with two or more digits after the decimal point, outside of photography 101 explanations of the subject.



If they do work in tenths of a stop, that's going to end up being kind of sloppy as a tenth does not go into a third. If they want to use some small fraction of a stop to work in, it ought to be one that is a divisor of the fractions they show publicly, so 1/6th (or any division there of: 1/12th, 1/18, etc).


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## tron (Jul 15, 2020)

SteveC said:


> If they do work in tenths of a stop, that's going to end up being kind of sloppy as a tenth does not go into a third. If they want to use some small fraction of a stop to work in, it ought to be one that is a divisor of the fractions they show publicly, so 1/6th (or any division there of: 1/12th, 1/18, etc).


This seems interesting! Back in the analog days EOS620 with Technical Back E could bracket in 1/4th of a stop steps!


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## tron (Jul 15, 2020)

1D4 said:


> It's amazing you looked through my post history and concluded I mainly argue with people. You should probably look again and not cherry pick the one or two times I've DISAGREED with someone who was making an illogical statement.
> 
> AGAIN, thanks for painting me as "forum police" when that's just because you totally misinterpreted (and continue to misinterpret) what I said. I'm done talking to you.


Although I agree with you mostly on 200-500 issue the price point is not illogical at all. Not everyone can pay a lot and if they already have a Nikon getting 200-500 is not illogical. There is no absolute truth you know.


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## Billybob (Jul 15, 2020)

YeTi73 said:


> D5, f/7.1 speed 1/1600s at morning, around 8 or 9, can't remember accurately.(for wild life that's a "good light condition", normally I do not walk around in the noon so does most of the animals)...chose f/7.1 to keep both birds in focus, Manual mode, ISO automatically boost to 6400.
> For online post or web use that's fine, but I do wish I could stay NO higher than ISO 3200, mainly because of the COLOR not the noise.
> 
> For M+Auto ISO, I use from EOS 1V, 5d Mark II, Mark IV...those combinations are different from flagship such as D5. That's my personal experience, but possibly I didn't study the user manual carefully, therefore I maybe use them "differently"


I didn't realize it was so easy to post files. These four were taken between 8:30 and 10am. The osprey shots were taken at f/8, 1/2000s and iso 800 and 2500. The lack of acuity is due to severe cropping rather than inadequate light. The other two shots were taken at f/7.1, 1/1600s, iso 800.

I'm not a big fan of auto ISO especially with cameras that are essentially ISO invariant above ISO 400 or 640. Thus, unless I totally blow the shot, it is easily correct in post. My experience with auto ISO is that it tends to raise the ISO too much. Of course, I could cap auto ISO at 1/3200, but I'm satisfied with my workflow. 

Again, I have no problem keeping my shots (much) below ISO 3200 even at f/7.1 and f/8.0. I have a good idea what ISO is appropriate for light conditions, so I rarely have to raise exposure more than 1 stop in post.


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## AlanF (Jul 15, 2020)

scyrene said:


> With all due respect that doesn't answer my question - if nobody can reliably tell a difference between 1/3 of a stop exposure change due to different apertures compensated by ISO or shutter speed, then how does it make a _practical difference_? I don't think 'nitpicking' is mischaracterisation of most of the discussion regarding differences between the two lenses.


This thread is: "*What is the maximum aperture at 400mm on the Canon RF 100-500mm f/4.5-7.1L IS USM?**"*
If you are not interested in discussing it because it is "nitpicking" and makes no practical difference, then fair enough, it's your choice. But, then why bother to post in it. Leave it to those who are interested in knowing.


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## AlanF (Jul 15, 2020)

Billybob said:


> I didn't realize it was so easy to post files. These four were taken between 8:30 and 10am. The osprey shots were taken at f/8, 1/2000s and iso 800 and 2500. The lack of acuity is due to severe cropping rather than inadequate light. The other two shots were taken at f/7.1, 1/1600s, iso 800.
> 
> I'm not a big fan of auto ISO especially with cameras that are essentially ISO invariant above ISO 400 or 640. Thus, unless I totally blow the shot, it is easily correct in post. My experience with auto ISO is that it tends to raise the ISO too much. Of course, I could cap auto ISO at 1/3200, but I'm satisfied with my workflow.
> 
> Again, I have no problem keeping my shots (much) below ISO 3200 even at f/7.1 and f/8.0. I have a good idea what ISO is appropriate for light conditions, so I rarely have to raise exposure more than 1 stop in post.


I too use manual for iso invariant regions, especially for birds in flight, erring on the side of under-exposure. It's especially important when the background lighting changes as the bird flies across it. It's easy to guess the exposure from experience or using the sunny 16 rule, and pushing through a couple of stops is the same as upping the iso by a couple.


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## PhotonShark (Jul 15, 2020)

Here's a super useful online exposure calculator.

Some example to get the equivalent exposure while retaining a given shutter speed.

f/5.6 at ISO 100 = f/6.3 at ISO 125 (133 rounded down)
f/5.6 at ISO 800 = f/6.3 at ISO 1000 (1066 rounded down)
f/5.6 at ISO 3200 = f/6.3 at ISO 4000 (4267 rounded down)

Exposure Calculator

Note : Values edited due to my error. Thanks AlanF for the unrounded and more accurate figures.


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## AlanF (Jul 15, 2020)

PhotonShark said:


> Here's a super useful online exposure calculator.
> 
> Some example to get the equivalent exposure while retaining a given shutter speed.
> 
> ...


I calculate that:
f/5.6 at ISO 100 = f/6.3 at ISO 133
f/5.6 at ISO 800 = f/6.3 at ISO 1066
f/5.6 at ISO 3200 = f/6.3 at ISO 4267
quite simply as f/6.3 = 1/3 stop higher than f/5.6 so multiply the f/5.6 value by 1.333 or 4/3. The calculator must be choosing a dialed in value for the camera, which is inaccurate.


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## PhotonShark (Jul 15, 2020)

AlanF said:


> I calculate that:
> f/5.6 at ISO 100 = f/6.3 at ISO 133
> f/5.6 at ISO 800 = f/6.3 at ISO 1066
> f/5.6 at ISO 3200 = f/6.3 at ISO 4267
> quite simply as f/6.3 = 1/3 stop higher than f/5.6 so multiply the f/5.6 value by 1.333 or 4/3. The calculator must be choosing a dialed in value for the camera, which is inaccurate.



My apologies, looks like I used the calculator incorrectly. I will edit my post. You can see the calculator shows rounded/nearest ISO values.


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## Eclipsed (Jul 15, 2020)

I'm pre-ordered, and indifferent to the minor differences in aperture between the generations. 

BUT, this is irritating. The reality is that a mechanical zoom lens with variable aperture will have a continuous function of aperture versus focal length, without steps. It will be f5.6 at only one focal length, faster at shorter, and narrower at longer. CANON, TELL ME WHAT THOSE NUMBERS ARE. It would be deceptive marketing to pretend that this is f5.6 at anything above the actual focal length at which it is 5.6. The fact that the display shows 5.6 does NOT mean it is "at" 5.6 at all those lengths. It might mean "at least 5.6" but I suspect not. I hope it doesn't mean "5.6 or less, but not as bad as 6.3".

I also fear that in the above example showing f5.6 from 254-363mm, we may be experiencing some anti-consumer deceptive rounding. I may be wrong, and would welcome being proven wrong, but if it's optically at 5.6 at 254, and f7.1 at the 363 transition point, this is unethical beyond rounding.

I also think it's unethical to sell a 383mm lens as 400.


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## bbasiaga (Jul 15, 2020)

marketing strikes again! but its not just canon, its everyone. And its not just this lens, its every one you've ever bought. 

-Brian


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## BeenThere (Jul 15, 2020)

Eclipsed said:


> I'm pre-ordered, and indifferent to the minor differences in aperture between the generations.
> 
> BUT, this is irritating. The reality is that a mechanical zoom lens with variable aperture will have a continuous function of aperture versus focal length, without steps. It will be f5.6 at only one focal length, faster at shorter, and narrower at longer. CANON, TELL ME WHAT THOSE NUMBERS ARE. It would be deceptive marketing to pretend that this is f5.6 at anything above the actual focal length at which it is 5.6. The fact that the display shows 5.6 does NOT mean it is "at" 5.6 at all those lengths. It might mean "at least 5.6" but I suspect not. I hope it doesn't mean "5.6 or less, but not as bad as 6.3".
> 
> ...


I think it’s industry practice to round off the numbers you are quoting. Have you ever seen a 383mm lens for sale? If it becomes too egregious, then the company reputation takes a hit, and reputation means a lot to the major manufacturers.


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## Eclipsed (Jul 15, 2020)

AlanF said:


> For those of us who are interested, it's not nitpicking but a desire to understand how our gear works and how to squeeze the best out of it. You don't have to understand much at all to get good images out of a camera or create works of art, but the technology is of great interest as well if you have a scientific bent.


Nor is it nitpicking when lenses that are a stop faster are double* the cost/value, and a 10%* shortfall in speed from what is marketed is real value.

*Examples for illustration.


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## Jack Douglas (Jul 15, 2020)

Eclipsed said:


> I'm pre-ordered, and indifferent to the minor differences in aperture between the generations.
> 
> BUT, this is irritating. The reality is that a mechanical zoom lens with variable aperture will have a continuous function of aperture versus focal length, without steps. It will be f5.6 at only one focal length, faster at shorter, and narrower at longer. CANON, TELL ME WHAT THOSE NUMBERS ARE. It would be deceptive marketing to pretend that this is f5.6 at anything above the actual focal length at which it is 5.6. The fact that the display shows 5.6 does NOT mean it is "at" 5.6 at all those lengths. It might mean "at least 5.6" but I suspect not. I hope it doesn't mean "5.6 or less, but not as bad as 6.3".
> 
> ...


383 - Perhaps, but looking around this world we live in I think there are infinitely more unethical things going on constantly that we live with, sadly.


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## AlanF (Jul 15, 2020)

Eclipsed said:


> Nor is it nitpicking when lenses that are a stop faster are double* the cost/value, and a 10%* shortfall in speed from what is marketed is real value.
> 
> *Examples for illustration.


The manufacturers are allowed a certain tolerance in defining the focal length and f-numbers of lenses. I once measured the front element of the 400mm f/4.O DO II to be about 95mm, and at least 100mm is needed for f/4. DxOMark measures its transmission to be equivalent to f/5.


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## sobrien (Jul 15, 2020)

Eclipsed said:


> I'm pre-ordered, and indifferent to the minor differences in aperture between the generations.
> 
> BUT, this is irritating. The reality is that a mechanical zoom lens with variable aperture will have a continuous function of aperture versus focal length, without steps. It will be f5.6 at only one focal length, faster at shorter, and narrower at longer. CANON, TELL ME WHAT THOSE NUMBERS ARE. It would be deceptive marketing to pretend that this is f5.6 at anything above the actual focal length at which it is 5.6. The fact that the display shows 5.6 does NOT mean it is "at" 5.6 at all those lengths. It might mean "at least 5.6" but I suspect not. I hope it doesn't mean "5.6 or less, but not as bad as 6.3".
> 
> ...



I don’t think variable aperture values are deceptive. There are swings and roundabouts. So, when an aperture value first changes that should mean that the actual aperture is wider than the value displayed - the value just happens to be the most proximate value. This is precisely what seems to be happening with the RF 100-500 - when it first moves to f/6.3 the reality is that it is f/6 or whatever at that point. Heck, given how little of this zoom range is at f/7.1 I wonder does it even reach f/7.1? Maybe Canon has undersold this lens?! 

The opposite is also true, though...as you get closer to the point where the value is about to increase the actual aperture is going to be higher than the value displayed. Some f/5.6 lenses might have a smaller aperture than f/5.6 but at least you know they will be closer to f/5.6 than f/6.3.

At least that’s how I understand these things to work.


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## tron (Jul 15, 2020)

AlanF said:


> The manufacturers are allowed a certain tolerance in defining the focal length and f-numbers of lenses. I once measured the front element of the 400mm f/4.O DO II to be about 95mm, and at least 100mm is needed for f/4. DxOMark measures its transmission to be equivalent to f/5.


I remember hearing about the less than real focal length tactic for lenses many decades ago but of course they would include f-numbers too.


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## sobrien (Jul 15, 2020)

Thinking about it a bit more, the actual/physical aperture of the 100-400 Mark ii at full extension could be something like f/5.9...i.e. above f/5.6 but closer to f/5.6 than f/6.3...and it might not really be 400mm as others have suggested...so taking those two things together it is possible that 100-400 Mark ii at full extension might have the very same physical aperture as the RF 100-500 _at that focal length_.

Edit in italics for clarification


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## blackcoffee17 (Jul 15, 2020)

I think i am happy with the 100-500 apertures. It's still 5.6 at 363mm, i think that's very decent. I am not so happy about the price, was hoping for something a bit cheaper, but the price was expected.


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## YeTi73 (Jul 15, 2020)

AlanF said:


> I calculate that:
> f/5.6 at ISO 100 = f/6.3 at ISO 133
> f/5.6 at ISO 800 = f/6.3 at ISO 1066
> f/5.6 at ISO 3200 = f/6.3 at ISO 4267
> quite simply as f/6.3 = 1/3 stop higher than f/5.6 so multiply the f/5.6 value by 1.333 or 4/3. The calculator must be choosing a dialed in value for the camera, which is inaccurate.


Sounds like you have a lot of calculation works to do. LOL
It's a one time thing or you'll do it every time? no offence, Just curious.
My normal concern would be, will the subject fly away, should I keep the shutter speed lower? For staying above 13000feet, a nose bleeding shooter, math and calculation are really no worries.


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## tron (Jul 15, 2020)

blackcoffee17 said:


> I think i am happy with the 100-500 apertures. It's still 5.6 at 363mm, i think that's very decent. I am not so happy about the price, was hoping for something a bit cheaper, but the price was expected.


I think Canon may have pushed that lens to the limits. Allow me to explain: They found the "worst" possible tolerable f-stop (f/8 would shock the 100-400 5.6II users - I am one of them -) the least possible acceptable telephoto boost over the 100-400, weight and size very close to 100-400 II and price maybe a little less than upper limit tolerable but which will make EOS Rxxx people "bite".

I know! if I ever upgrade to EOS R5 from my EOS R I would be tempted! OK I would wait for the price to become lower. I am not letting go of my EF teles and/or my 500mmPF any time soon!


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## AlanF (Jul 15, 2020)

YeTi73 said:


> Sounds like you have a lot of calculation works to do. LOL
> It's a one time thing or you'll do it every time? no offence, Just curious.
> My normal concern would be, will the subject fly away, should I keep the shutter speed lower? For staying above 13000feet, a nose bleeding shooter, math and calculation are really no worries.


 I spent years looking at my grad students calculations and seeing and checking numbers is second nature. Trouble is that I also have to check facts that puzzle me. Geekish, but I like understanding things. But I like photographing birds and nature far more.


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## AlanF (Jul 15, 2020)

Can anyone remember seeing the patent for the 100-500mm? They sometimes have the real focal lengths and apertures on them.


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## YeTi73 (Jul 16, 2020)

CJudge said:


> That's what I'm talking about too. Unless I'm still misunderstanding you...
> 
> No matter what shooting mode you are in, when you go into the ISO selection, you can always pick "auto". I often use that when shooting events, because I want to control the other two factors, but the changing light conditions make auto ISO helpful for staying in the correct exposure ball-park.


Yes, you're right  I was wrong on that. EOS 1V, 5D2, don't know how to do that, but the trick works on 5d4.
where is my cognitive bias came from then???


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## jolyonralph (Jul 16, 2020)

sobrien said:


> Thinking about it a bit more, the actual/physical aperture of the 100-400 Mark ii at full extension could be something like f/5.9...i.e. above f/5.6 but closer to f/5.6 than f/6.3...and it might not really be 400mm as others have suggested...so taking those two things together it is possible that 100-400 Mark ii at full extension might have the very same physical aperture as the RF 100-500 _at that focal length_.
> 
> Edit in italics for clarification



Probably not, but they're close.

They are rounded down (marketing) so at 1/3 stop intervals something listed as f/5.6 will have a true f value between 5.657 and 6.350

At 1/2 stop intervals the f/5.6 range is 5.657 to 6.727

So, as the EF 100-400 shows f/5.6 at 400mm even on 1/3 stop we can be sure that the actual f value will be between 5.657 and 6.350

Looking back at the EF 100-400 patents (I'm not entirely sure which one is the correct one for the II) shows the f stop at 391mm (the real maximum) is either f/5.8 or f5.85 

On the RF 100-500 at 400mm it has to be between 6.350 and 6.727 - which means you're probably looking at around 1/4 of a stop of light reduction - maybe less (especially if you measure at 391mm instead of 400mm).

In any case, the increase in light at the wider range of the lens plus the longer reach and faster focusing surely makes up for this!


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## tron (Jul 16, 2020)

What IFs are useless but if only Canon made it with just a little larger diameter (and give it a front filter ring of 82mm instead of 77mm so doable) it most probably would be f/6.3 instead of f/7.1 and at the same time it would be f/5.6 at 400mm. But that would impose a toll on its weight so there is that.


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## AlanF (Jul 16, 2020)

I just measured the focal length of the 100-400mm II. At a distance of 19.5m and set at 400mm on my 5DSR, the calculated focal length is 383mm, which is in agreement with figures presented here (you can check my calculations: a horizontal line 138mm long at a distance of 19.5m gives an image 681px wide on the sensor, which is 36.0mm and 8688px wide).


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## BeenThere (Jul 16, 2020)

tron said:


> What IFs are useless but if only Canon made it with just a little larger diameter (and give it a front filter ring of 82mm instead of 77mm so doable) it most probably would be f/6.3 instead of f/7.1 and at the same time it would be f/5.6 at 400mm. But that would impose a toll on its weight so there is that.


+$1000.


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## tron (Jul 16, 2020)

BeenThere said:


> +$1000.


Terrifying but correct I guess!


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