# Canon 400mm L 5.6 .. So what's changed in 19 years?



## revup67 (Jul 6, 2011)

This great lens first released in 1993 is currently still part of Canon's lineup and tack sharp. It has USM but lacking IS as most of us know. I called Canon support (3 different reps) and no one was able to tell me what exactly has changed/updated/upgraded on this lens since 1993. It would seem logical that some components have been upgraded or possibly the coating but not necessarily a feature accessible by consumers.

Does anyone or can anyone shed any light on the 19 year time line for this lens? 

PS one thing Canon support did state is that the lens is "drip and dust proof" which debunked a statement I had found on another web site.
Thanks in advance
Rev


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## drummstikk (Jul 6, 2011)

I'm sure this lens was coated from day one. Coating has been standard on even the "non-premium" lines of OEM lenses since the 1970's or earlier. Although I suppose coating might improve to some incremental degree. Probably nothing else has changed about the 400 f/5.6 since it's inception other than possibly the sourcing of small components, as you suggest.

IS would be nice, but I don't find I miss it much in my use, which usually includes a monopod. I actually wish it was a bit heavier or fatter, as that might make it settle in your hands more steadily for hand-holding. But overall, no complaints.

It's not likely, but I wish Canon would upgrade this lens with IS and maybe take it to f/4.5 or so to give it just a bit more speed and heft. An f/4.0 lens would obviously command a price tag much higher than the current 5.6. What could we get with IS for, say, $2000.00 to $2400.00? f/4.5? 5.0?

Come on, Canon. Make me an offer.

Back in the day, Olympus had a few "big white" lenses in odd focal lengths and fast apertures. 250mm f/2.0, 350mm f/2.8 and maybe a 450mm f/2.8 (not sure, it's been a long time).

I'd go for a 350mm f/4.0 with IS. (Compared to the 400mm f/5.6, I'd gladly trade 50mm and some money for a full f/stop.) Or a 250mm f/2.8, which would be 350mm f/4.0 with a 1.4x. Or, I've long wished they would extend the 70mm-200mm 2.8 to 250mm. But that's just me dreaming. CR ZERO.

Anybody with me, or am I just weird?


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## dr croubie (Jul 6, 2011)

They canned the original 200 f1.8 becuse of ROHS concerns, nothing in the glass, but the manufacturing process made some nasty by-products. They couldn't change the composition/manufacturing process easily, so they came up with the 200 f2.

That hasn't happened with the 400 f5.6, so i'd be very doubtful that they've changed the composition of any glass. There were no ultra-special elements like the 200/1.8, and they wouldn't just change any pieces of glass without putting a II after it. Maybe they could have quietly changed a coating for a bit better performance, or more likely for a cost saving.

There's no IS to update to a better design. The USM is possible to have been changed to a slightly better/quieter/faster design, or at least they might have made it cheaper to make.


But companies like canon will take any excuse to put a II behind the name of any lens. It's good marketing if people think their lens has been designed last year rather than 5, 10, 20 years ago (case in point, the efs55-250 ii, whether this is a recent phenomenon is debatable). If they just quietly updated everything without telling, people would keep their old stuff, and yell that their R&D dept does nothing.

So my money's on absolutely nothing having changed, bar a slightly cheaper process for some minor parts...


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## revup67 (Jul 6, 2011)

thanks for the replies and my statements were only examples about the glass or the coating as sort of a reference. Assumptions welcome but I was seeking more absolute, factual information if at all possible.


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## kubelik (Jul 6, 2011)

the factual information is exactly what dr croubie pointed out: the fact that there is no factual information to be found.

croubie nails it on the head when he states that what can be charged for won't be given away for free. also, when you're dealing in the photography industry, don't expect that everything is announced somewhere. for instance, discontinued production is almost never announced formally; you won't be able to get on a search engine and determine when canon ran the last batch of a particular lens.


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## Mt Spokane Photography (Jul 6, 2011)

Some of us prefer to get a $1500 lens that is excellent to the same lens for $2500 that is ever so slightly sharper, and has better IS.

In a way, its a good idea to keep making those old lenses that are sold at relatively low prices compared to what their replacements will cost.

I'm always wanting better lenses, just like everyone else, but i'd hate to see the prices go up by $1,000 more or less.


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## ReyMorlu (Jul 6, 2011)

With the exception of the tripod collar, now more likely 70-200 shaped against the square shaped minimalist older one... and unconfortable in xtrem! I have not had any other info about it and believe me, I'm specting Canon to decide updating this lens for a long time!!
Then I read all about it wherever, but it seems this brand prefer not to sale this lens! :-\ cause nobody who has tested the "IS" in other lenses do not have any interest in non-is lenses and when you need a long specific focal lenght, zooms are not good enough to give the spected image quality.(100-400 ie)
Another question is the price paid... why when is added to a pro lens it doubles its price and amateur lenses have "is" at afordable low prices????? (300/4 & 300/4 IS, another example)


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## neuroanatomist (Jul 6, 2011)

Canon has done some 'stealth' updates, but they are always minor changes (e.g. slightly faster AF chip, when the subcontractor stopped producing the previous one or they changed contractors, for example). New coatings mean sharper lenses with better MTF curves - Canon would not let those out the door without a corresponding MkII designation (and more importantly, a price increase).



revup67 said:


> one thing Canon support did state is that the lens is "drip and dust proof" which debunked a statement I had found on another web site.



The rep you spoke with was incorrect. The 400mm f/5.6L USM is not a weather-sealed lens. Sealed lenses are easily identified by the black rubber seal at the lens mount, and the 400/5.6 does not have one of them - therefore, not sealed. 



drummstikk said:


> I wish Canon would upgrade this lens with IS and maybe take it to f/4.5 or so to give it just a bit more speed and heft. An f/4.0 lens would obviously command a price tag much higher than the current 5.6. What could we get with IS for, say, $2000.00 to $2400.00? f/4.5? 5.0?
> 
> I'd go for a 350mm f/4.0 with IS. (Compared to the 400mm f/5.6, I'd gladly trade 50mm and some money for a full f/stop.) Or a 250mm f/2.8, which would be 350mm f/4.0 with a 1.4x. Or, I've long wished they would extend the 70mm-200mm 2.8 to 250mm. But that's just me dreaming. CR ZERO.
> 
> Anybody with me, or am I just weird?



For $2K, you'll be lucky to just get the 400mm f/5.6 with IS - I'd guess that lens, if released, will come in at ~$2200. Even at that price, I'd buy one straight off.

I think lots of people are with you - we all want more (wider aperture, longer focal length) for less $. But what I think you're missing is the practical barrier. Do the math: 400mm/5.6 = 71.5mm, 300mm/4 = 75mm, 200mm/2.8 = 71.5mm, etc. The lenses you're talking (dreaming) about all push that iris diaphragm up over 75mm, meaning an increase in the diameter of the front element beyond 77mm threads. They could give you a 420mm f/5.6 (same iris diaphragm diameter as the 300mm f/4), but the extra 20mm probably isn't worth it. Bigger glass means more cost. Those fast Oly lenses you mention were close in price to the Canon superteles, e.g. the Oly 250mm f/2 was $4300 and the Oly 350mm f/2.8 was $5500.


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## dr croubie (Jul 6, 2011)

ReyMorlu said:


> cause nobody who has tested the "IS" in other lenses do not have any interest in non-is lenses



google translate issues aside, i can definitely agree.
a 250 f/3.5 MF prime i've got is just hand-holdable focussable, despite its soviet-stiffness in the ring. add a 2x tele for 500 f/7 and i can barely frame and focus, lack of a tripod ring and gimball head doesn't help. I could maybe put up with 400 f/5.6 without IS, but it'd have to be some damn sweet IQ to make up for the annoyance.

(and if i add my two 2x teles for 1000mm f14, just breathing on the lens to focus will shoot the framing off, so not very useful even in studio work, but it sure looks impressive with all my extension tubes)


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## neuroanatomist (Jul 6, 2011)

ReyMorlu said:


> Another question is the price paid... why when is added to a pro lens it doubles its price and amateur lenses have "is" at afordable low prices????? (300/4 & 300/4 IS, another example)



If your reference to the 300/4 vs. 300/4 IS was an example of a lens doubling in price, it's not a good example - after compensating for 6 years of inflation, the IS version of the lens was a price increase of only 14%. 

The reason that addition of IS to 'pro' lenses is differentially more than 'amateur' lenses is that pro lenses have wider apertures for comparable focal lengths, meaning bigger lens elements, including the IS elements. Bigger elements cost more, and require more powerful (and thus expensive) motors to move them. An 18-55mm f/3.5-5.6 IS lens has an IS element group that is ~15mm in diameter. The 300mm f/4L IS has an IS element group that is ~37mm in diameter, and therefore contains approximately _5 times_ as much glass as the elements in the 18-55mm lens.


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## Mt Spokane Photography (Jul 6, 2011)

neuroanatomist said:


> For $2K, you'll be lucky to just get the 400mm f/5.6 with IS - I'd guess that lens, if released, will come in at ~$2200. Even at that price, I'd buy one straight off.



I'd likely do it as well, but the sad thing is, if all the lenses took a jump in price like this, a lot of photographers would not be able to afford one, and that would be a shame.

Perhaps they should come out with a totally new model and keep the old one like they did with the 70-200 models.


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## WarStreet (Jul 6, 2011)

ReyMorlu said:


> ... cause nobody who has tested the "IS" in other lenses do not have any interest in non-is lenses


I just purchased the 400mm 5.6, and I do have the great IS of the 70-200 2.8 IS II for which I switch it off very often, and these lenses are used handhold. It depends on the usage needs. I didn't used the 400mm for my intended use for now, as I will do so within few months, and also since I have a focusing problem and I am currently dealing with Canon to fix it. But from the few test, this lens is great, and I like it since it gives me what I want without IS.

I do like IS and I think Canon have the best stabilisation on the market, but it has a big disadvantage which gets ignored when comparing optical stabilisation against sensor shift, which is the quality/price ratio value. We have to look at the quality we are missing due to IS. If Canon have created a new non stabilised 70-200 2.8 costing the same as the 70-200 2.8 IS II, the lens would have been optically better than the IS version.

I am not saying that sensor shift is better than optical stabilisation, since this is subjective, but this is a disadvantage which has to be considered. Without IS, they could have created a slightly lower priced with slightly higher quality lens by using the advantage of the quality/price ratio.


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## revup67 (Jul 7, 2011)

Hello Neuro (you wrote): "The rep you spoke with was incorrect. The 400mm f/5.6L USM is not a weather-sealed lens. Sealed lenses are easily identified by the black rubber seal at the lens mount, and the 400/5.6 does not have one of them - therefore, not sealed. "

I wanted to inquire again and gain further specifics on this previous support statement and spoke with another Canon rep (Larry) who read out of the in house tech support lens catalog this lens only offers drip and dust proof sealing when attached to an EOS 1D and no other camera. it is inherent and directly to a seal only found on the EOS 1D and no other. Bummer.


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## dr croubie (Jul 7, 2011)

...and don't forget that sensor shift has problems with overheating, but we've heard that story before...

also, don't forget *The Third Option*, if only canon would make something like that.
but they won't, because then people would buy the 70-200 nonIS and the converter for less than the price of the 70-200IS (if it worked as good, that is). I'd even buy one for all my old MF primes, if it worked half as good as a canon IS, just for framing...


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## neuroanatomist (Jul 7, 2011)

revup67 said:


> Hello Neuro (you wrote): "The rep you spoke with was incorrect. The 400mm f/5.6L USM is not a weather-sealed lens. Sealed lenses are easily identified by the black rubber seal at the lens mount, and the 400/5.6 does not have one of them - therefore, not sealed. "
> 
> I wanted to inquire again and gain further specifics on this previous support statement and spoke with another Canon rep (Larry) who read out of the in house tech support lens catalog this lens only offers drip and dust proof sealing when attached to an EOS 1D and no other camera. it is inherent and directly to a seal only found on the EOS 1D and no other. Bummer.



Interesting...so, it's sealed only when used with a camera that was discontinued at the end of 2003. Well, if true, that's certainly not very useful. 

I'm still not certain that's true - tech manuals are occasionally incorrect. Statements like that have been used on many weather sealed lenses, becuase technically, only the 1-series bodies are truly sealed against dust and moisture. 

I still believe that the lens mount gasket is necessary for sealing - the mount surface on a 1D body (or any other body) does not have an exterior gasket.

I'll do a little more digging...


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## drummstikk (Jul 7, 2011)

neuroanatomist said:


> For $2K, you'll be lucky to just get the 400mm f/5.6 with IS - I'd guess that lens, if released, will come in at ~$2200.



Yeah, yer right. I was kind of lowballing the price. I got my 400mm f/5.6 used for about $950.00, so that distorted the starting point in my mental math.

My main point, though, was that I'd like to see Canon and others (Sigma, etc.) think a little more outside the box (to use a detestable corporate cliche') in terms of focal lengths of long tele fixed lenses. 

There is a lot of innovation in zoom ranges, but we keep getting all the same fixed tele lenses over and over (300-400-500-600). Here's what I keep thinking: I already have the 70-200 f/2.8, and I want another longer lens for more reach. The 300 f/4.0 is a very good lens, but I can't get really excited about it since I have essentially the same thing if I put my 1.4x on the 70-200. The next choice up is the 400mm 5.6, which I own and love, but it's too tight for quite a few things while on the 7D in addition to being a slow f/5.6. As I said in an earlier post, I'd love to trade 50mm and some money to get that extra f/stop (4.0), and the lens would then be differentiated from what I get with the 70-200 + 1.4X. Putting the 1.4X on a 350mm f/4.0 would yield an attractive (rounded off) 500mm f/5.6.

Here, I'm mainly talking about the "mid-level" L lenses (300mm f/4.0, 400mm f/5.6). I'm not sure the same thinking applies the "big whites" (300mm f/2.8, 400mm f/2.8, etc.). The 300mm f/2.8 is already differentiated from 70-200 + 1.4X because it is f/2.8, rather than f/4.0 with the zoom combo.


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## neuroanatomist (Jul 11, 2011)

neuroanatomist said:


> revup67 said:
> 
> 
> > Hello Neuro (you wrote): "The rep you spoke with was incorrect. The 400mm f/5.6L USM is not a weather-sealed lens. Sealed lenses are easily identified by the black rubber seal at the lens mount, and the 400/5.6 does not have one of them - therefore, not sealed. "
> ...



Apparently, the 400mm f/5.6L is partially sealed. According to Chuck Westfall (Canon's tech support guru), "_The EF400mm f/5.6L USM lens was designed before Canon started offering "dust and drip resistant" lenses, so it does not have a mount gasket or a built-in protective filter. However, it does have seals under the switches and the focusing ring, so it is weather-resistant to a point._" A UV/clear filter on the front would substitute for the built-in protective filter (something that's found on most current supertelephoto lenses, which have front elements too large for a threaded filter). However, I don't see anything really compensating for the lack of the mount gasket on the 400mm f/5.6L. Without that gasket, the contact with any body, including a 1-series, is metal-to-metal with no surrounding seal, meaning there is the potential for water to enter.


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## WarStreet (Jul 11, 2011)

neuroanatomist said:


> The EF400mm f/5.6L USM lens was designed before Canon started offering "dust and drip resistant" lenses, so it does not have a mount gasket or a built-in protective filter. However, it does have seals under the switches and the focusing ring, so it is weather-resistant to a point



This means that it is 100% sealed for dust, and partially sealed for drips, right ?


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## neuroanatomist (Jul 11, 2011)

WarStreet said:


> neuroanatomist said:
> 
> 
> > The EF400mm f/5.6L USM lens was designed before Canon started offering "dust and drip resistant" lenses, so it does not have a mount gasket or a built-in protective filter. However, it does have seals under the switches and the focusing ring, so it is weather-resistant to a point
> ...



Not sure. I'd interpret it as partially sealed for both dust and moisture - partial because the lens/body junction is not sealed at all.


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## dr croubie (Jul 11, 2011)

I'd read it as
'sealed for drips/dust getting into the lens itself and between glass elements' +
'not sealed for anything getting between the lens/camera mount'.

the first one is good, noone wants dust between their elements, but it's not the end of the world if you do. the second one, yeah, that could be the end of the world if you get water in there. I've used my 7D in slight rain with 15-85, nothing bad happened, but it wasn't a downpour.
but no camera is perfectly sealed unless you buy those indestructible P&S, so there's no substitute for common sense and treating nicely. I found that out the hard way...


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## Edwin Herdman (Jul 17, 2011)

Funny that the latest (so it would seem) reference available to Canon techs about the lens is dating from the original 1D.

IS aside, and maybe some lens production aside, Canon doesn't seem to have a big reason to update this lens. I still see lots of people mentioning they use it here and there, and it seems a pretty good bang for the buck.

What's changed since the lens was released is the advent of Diffractive Optics...oh, nevermind. (The 200-400mm DO IS USM and the 500mm f/2.8 are still AWOL, and nothing else has come of the technology, still, besides the 70-300mm DO.)

Something I thought was interesting was the 400mm f/4 comparison lens (a mockup? or a rival prototype?) Canon used in its early promotional material (still available around the web where the press release is mirrored, i.e. DPR) which looked identical to the DO lens but just longer. I would think that moving from f/5.6 to f/4 would be highly worthwhile and would add some speed to AF without quite reaching f/2.8L prices - but realistically, Canon only needs to have the f/5.6 for people who are really pressed for cash but need a 400mm option (usually those who would rather have a 500mm f/4 or longer, I suspect). People who want AF speed and better background blur have at least two newer-than-the-5.6L choices in f/2.8L lenses. The f/4 DO is probably not as good as a non-DO f/4 but they have little reason to create another lens with that focal length and aperture. I think the 400mm f/5.6 is going to be played out until it becomes really embarrassing to the line in terms of sharpness - somewhat like the 100-400mm L which is still selling like crazy and has no replacement in sight (even thought the new 70-300mm L shows it's quite possible to better it optically).


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## kubelik (Jul 18, 2011)

I like edwin's comment about a 400 f/4 ... I'd like that, which I could then stick a 1.4x on top of to get a cheap-ish, easy 560 f/5.6, or just a straight 500 f/5.6 ... which would definitely save some cost and probably also some weight.


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## Mt Spokane Photography (Jul 18, 2011)

kubelik said:


> I like edwin's comment about a 400 f/4 ... I'd like that, which I could then stick a 1.4x on top of to get a cheap-ish, easy 560 f/5.6, or just a straight 500 f/5.6 ... which would definitely save some cost and probably also some weight.



Which 400mm f/4 are you discussing? The existing one is not cheap, and does not take TC's particularly well. A new 400mm f/4 would certainly be in the $7,000 range.


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## kubelik (Jul 18, 2011)

I wasn't discussing the existing 400 f/4, whose price is blown way out of line because of the DO. I think a 400 f/4 L IS could easily fall into the $5K or $6K range (even $7K would mean plenty of people would buy this over a 400 f/2.8 monster) ... 

I'll get back on my favorite topic: as I've stated a number of times before, I think the ideal lens for telephoto prime in the prosumer range would be a 500mm f/5.6 L IS. you could do that for probably around $2K to $3K, meaning it would be a great entry-level supertelephoto L lens for the prosumer crowd. it would be a relatively light and cost-effective means of getting to 500mm and still be able to have it AF with any body ... which right now, simply doesn't exist. you have to go to sigma and buy an optically poor zoom to get you to 500mm for the time being on a non-1-series body.


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## WarStreet (Jul 18, 2011)

A 400mm f4 non DO would be great. We have the 300mm 2.8 + TC for this, but if we need 400mm, getting the native FL is better. The price of the 400mm f4 would be similar to the new 300mm 2.8 IS II, about $7000 release price.

I did considered The 400 DO since the low weight was a great advantage, but the reason for such a lens for me would be to get more background blur quantity, but unfortunately, this lens has horrible bokeh, so it defeats the purpose.


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## Edwin Herdman (Jul 19, 2011)

Random guess about a possible reason Canon avoids a 500mm f/5.6: Canon would want to avoid cheapskates (like me) from buying such a lens and then complaining about its "poor autofocus performance" when they use it on cheap Rebel (#00D) bodies. The 500mm f/4 is expensive, but I bet that stop of light gained would be a big benefit. I know that my cheap-o Sigma 120-400mm has a tough time focusing on stuff at 400mm (where it is f/5.6).

And on the other hand, while the price savings would probably be substantial, I wouldn't be surprised if it still wasn't enough to really satisfy cheapskates, and pros would generally rather stick to their f/4 aperture.


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## kubelik (Jul 19, 2011)

@edwin: I don't know much about lens optics. would a 500 f/5.6 be darker than a 400 f/5.6? from what I've heard, the 400 f/5.6 is a pretty good lens as far as AF speed and accuracy go, so would keeping the same max aperture really hurt that? I do understand we're dealing with shallower depth of field because of the focal length, how big of a deal is that?


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## neuroanatomist (Jul 19, 2011)

kubelik said:


> @edwin: I don't know much about lens optics. would a 500 f/5.6 be darker than a 400 f/5.6? from what I've heard, the 400 f/5.6 is a pretty good lens as far as AF speed and accuracy go, so would keeping the same max aperture really hurt that? I do understand we're dealing with shallower depth of field because of the focal length, how big of a deal is that?



A 500mm f/5.6 would project the same amount of light on the image and AF sensors as a 400mm f/5.6 - that's solely a function of iris diaphragm diameter (89.3mm for 500/5.6, 71.4mm for 400/5.6). 



Edwin Herdman said:


> Random guess about a possible reason Canon avoids a 500mm f/5.6: Canon would want to avoid cheapskates (like me) from buying such a lens and then complaining about its "poor autofocus performance" when they use it on cheap Rebel (#00D) bodies. The 500mm f/4 is expensive, but I bet that stop of light gained would be a big benefit. I know that my cheap-o Sigma 120-400mm has a tough time focusing on stuff at 400mm (where it is f/5.6).



The stop of light is a benefit gained for shutter speed, no effect on AF performance. For anything other than a 1-series body, the off-center AF point sensors are f/5.6-sensitive - an f/4 lens does not provide any additional sensitivity or accuracy - an f/4 lens is the same as f/5.6 for the AF system. The center AF point on recent non-1-series bodies is f/2.8 sensitive, so f/4 doesn't help there, nor does faster than f/2.8. For a 1-series body it would make a difference - the high-precision center AF point on those bodies is f/4-sensitive.

Sorry, Edwin - your Sigma 120-400mm has a tough time focusing on stuff at 400mm (where it is f/5.6) not because it's f/5.6, but because it's a cheap-o lens and the AF system in the lens is not that good.


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## dr croubie (Jul 19, 2011)

neuroanatomist said:


> Sorry, Edwin - your Sigma 120-400mm has a tough time focusing on stuff at 400mm (where it is f/5.6) not because it's f/5.6, but because it's a cheap-o lens and the AF system in the lens is not that good.



I'll certainly vouch that my 15-85 @ 85mm and 70-300L @ 300mm (both at f/5.6) have no troubles focussing in all but the darkest rooms. 50 f/1.8 isn't so bad (because it's fast), but 70-300nonL @ 300mm occasionally had some troubles in a bit of darkness, lower quality AF than the L-version...


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## Edwin Herdman (Jul 19, 2011)

neuroanatomist said:


> The stop of light is a benefit gained for shutter speed, no effect on AF performance. For anything other than a 1-series body, the off-center AF point sensors are f/5.6-sensitive - an f/4 lens does not provide any additional sensitivity or accuracy - an f/4 lens is the same as f/5.6 for the AF system. The center AF point on recent non-1-series bodies is f/2.8 sensitive, so f/4 doesn't help there, nor does faster than f/2.8. For a 1-series body it would make a difference - the high-precision center AF point on those bodies is f/4-sensitive.
> 
> Sorry, Edwin - your Sigma 120-400mm has a tough time focusing on stuff at 400mm (where it is f/5.6) not because it's f/5.6, but because it's a cheap-o lens and the AF system in the lens is not that good.


It is a cheap-o lens, no argument there! AF is a rather complicated topic, but here is my reasoning:

1.) The "tape trick" enables autofocus, albeit slowly, with apertures slower than the "hard limits" (which are really just soft limits) of the camera. (Though, to be fair, we've gone from a lens-assisted AF to one where only the camera body is guessing at it, so that's not definite proof.)

2.) Even good lenses have trouble autofocusing in low light. (Which would seem analogous to moving up steps in aperture somewhere between f/2.8 and f/5.6 or f/8.)

There are plenty of anecdotes, like this from The Digital Picture:


> Another negative aspect to shooting with the Canon EF 1.4x II Extender attached is the resulting reduction in autofocus speed. This can be an issue if you are shooting in low light and/or are using a lens that is not very fast focusing (such as the Canon 180 L lens mentioned above).


That would be a reduction from f/3.5 to f/5 - neither f-number is at or passing any limits in sensitivity of the autofocus system. The problem with that example being used to prove my particular theory is that the teleconverter's AF chip is used, not the 180 Macro's.

More relevant, but gratingly unsourced, this from the Wikipedia article on autofocus:


> The speed of the AF system is highly dependent on the maximum aperture offered by the lens. F-stops of around f/2 to f/2.8 are generally considered optimal in terms of focusing speed and accuracy. Faster lenses than this (e.g.: f/1.4 or f/1.8) typically have very low depth of field, meaning that it takes longer to achieve correct focus, despite the increased amount of light.


If true, that's essentially exactly what I'm saying.

I suppose the argument that absolute aperture doesn't matter would be that the AF zone system works like the grid on a default bright focusing screen for viewfinders, which do not demonstrate real DOF effects at apertures wider than around f/2.8, regardless of how much faster the lens really is, and furthermore don't appear to get dimmer until you stop down past f/2.8.

Looking again I see the 120-400mm is a fairly old lens (c. 2001-ish). Sigma has been known to rechip lenses with newer AF parts, and I don't know the date of manufacture. It's probably a fairly recent make though (bought off Amazon at the beginning of 2011).

I'm curious...did you have any tests or sources available that confirm what you're saying? I've had limited experience thus far with autofocus but even that little seems enough to confirm my suspions all along.

It will be interesting to see what happens when I get that 2X extender, which will make the maximum aperture of the new 120-300mm f/2.8 OS roughly equivalent to the maximum aperture of the 120-400mm OS. (Would be yet more interesting to compare it with the Sigma version's AF; alas, I have no Sigma version on hand...if I need the Sigma version, that'll mean I have no lens compatible with the Canon 2X III for doing a direct comparison of the two teleconverters and their effects on autofocus, however.)

I would certainly be most comfortable agreeing that the actual AF systems involved can have a sizable impact on AF performance, but when you start gaining or losing a stop or more, even the best AF detection routines are likely to be taxed.


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## Edwin Herdman (Jul 20, 2011)

Update: It's not the lens, it's the camera...the 120-300 f/2.8 still hunts now and then in more or less the same situations that the 120-400mm did. Now I'm interested to see what a better AF sensor would do.


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## neuroanatomist (Jul 20, 2011)

Edwin Herdman said:


> Update: It's not the lens, it's the camera...the 120-300 f/2.8 still hunts now and then in more or less the same situations that the 120-400mm did. Now I'm interested to see what a better AF sensor would do.



Ok, so not a cheap-o lens. But still, a Sigma lens, and Sigma has to reverse-engineer the AF algorithms, plus the fact that Sigma lenses are often reported as having less than stellar AF. So, frankly, I'm still not convinced it's the camera. Does a Canon lens of the same aperture hunt like the Sigmas do?


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## kubelik (Jul 20, 2011)

here's why I believe a 500mm f/5.6 L IS would have pretty good AF speed and accuracy:

1. people have been highly complementary of the Canon 400mm f/5.6 L, which we've noted is the same max aperture

2. my 70-200mm f/2.8 L IS II on a 5DII body focuses pretty quick except in extremely low lighting situations. most people agree that a native f/5.6 lens will AF better than an f/2.8 lens + 2x extender, so if the 70-200 is already pretty good, a 500 f/5.6 would be better.

that's good enough for me, and I suspect for almost anyone interested in buying a 500 f/5.6


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## neuroanatomist (Jul 20, 2011)

kubelik said:


> most people agree that a native f/5.6 lens will AF better than an f/2.8 lens + 2x extender, so if the 70-200 is already pretty good, a 500 f/5.6 would be better.



The accuracy should be equivalent with and without extender. But using the 2x extender will result in ~50% slower AF, by design, than the bare lens; a 1.4x extender slows AF speed by ~25%, also by design.


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## autochrome (Jul 20, 2011)

On the weather sealing issue, seems all pre-1999 lenses have some basic form of weather sealing:



> Chuck Westfall (Canon USA) has provided information about the weather sealing found in some pre-officially-sealed lenses.
> 
> According to Mr Westfall, *"Pre-1999 white EF lenses such as the 200/1.8L, 300/2.8L, 300/4L, 300/4L IS, 400/2.8L, 400/5.6L, 500/4.5L, 600/4L, 35-350/3.5-5.6L, 70-200/2.8L, and 100-400/4.5-5.6L all lack mount gaskets but have moderate dust and moisture resistance for their switches, focusing rings and zoom rings where applicable."*
> 
> ...


http://www.the-digital-picture.com/News/News-Post.aspx?News=996&Title=Partially-Weather-Sealed-Canon-Lenses


The 400mm f5.6L is tempting. Sure the IS would be nice, but the price would jump from 1300 euros to 2500 at least, that's almost certain (if not more, judging by the massive leap in price in the latest super telephotos with the addition of IS mode 3) - and this when Canon decides it's time to update it, which probably won't happen soon. Everything considered it seems the best bargain around, price and optical quality considered. The lack of full weather sealing is another annoyance though. Other ones that also need weather sealing are the 35mm f1.4L, 85mm f1.2L, 200mm f2.8L II, 180mm f3.5L macro and 135mm f2.0L at least, some of which were rumoured to be replaced here (the 35mm and the 135mm if i remember it well).


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## neuroanatomist (Jul 21, 2011)

autochrome said:


> On the weather sealing issue, seems all pre-1999 lenses have some basic form of weather sealing:
> 
> 
> 
> ...



Yep. In fact, it was this very thread that resulted in the news post on Bryan's TDP site. From p.2 of this thread:



neuroanatomist said:


> neuroanatomist said:
> 
> 
> > I'll do a little more digging...
> ...



My 'digging' consisted of contacting Mr. Westfall, and I forwarded his responses to initial and follow-up questions to Bryan at TDP (John = me, neuroanatomy is part of my day job  ), thinking the fact that these 'unsealed' lenses do have partial sealing was pretty interesting and worth disseminating. In particular, the fact that a push-pull zoom like the 100-400mm actually has dust-resistant seals around the zoom ring is worth noting, since that lens is sometimes aka the "dust pump."



autochrome said:


> Other ones that also need weather sealing are the 35mm f1.4L...



I agree...but remember that for sealing on a lens to be effective, the body must also be sealed, and although some non-1-series bodies have partial sealing, only the 1-series are truly weather-sealed (the rank ordering for sealing is 1-series >> 7D > 5DII = 50D/60D).


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## autochrome (Jul 21, 2011)

neuroanatomist said:


> autochrome said:
> 
> 
> > On the weather sealing issue, seems all pre-1999 lenses have some basic form of weather sealing:
> ...



somehow i missed that



> neuroanatomist said:
> 
> 
> > neuroanatomist said:
> ...



I see  You're the person that asked about the gasket retrofitting? That would've been great to have, even unnoficially, or even implying voiding the warranty.



> autochrome said:
> 
> 
> > Other ones that also need weather sealing are the 35mm f1.4L...
> ...



At the moment i have a 7D. I thought about a 2nd body, a 5D Mk.II, but resisted the temptation and invested in lenses instead. I'll skip the 5D Mk.II and get a 1D when the time is right.
In fact i just got the 400mm, lack of full weather sealing and all. I thought the lack of IS would make it unusable (since it's a 640mm equivalent on APS-C), but it's not that bad. I'll just have to get some sort of weather protection when using it outdoors, other than this issue, my first impressions are positive. The 100-400mm was too cumbersome, i would be using it at 400mm mostly, and i got the 70-200mm range covered already. I'm not sure the 400mm f4.0 DO is fully weather sealed, but at the price Canon is charging for the DO you can make a bit of extra effort and go straight to the 500mm which is a far better investment (and would be even better if it included a chiropractor ).


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## neuroanatomist (Jul 25, 2011)

autochrome said:


> I see  You're the person that asked about the gasket retrofitting? That would've been great to have, even unnoficially, or even implying voiding the warranty.



No, Bryan asked about the retrofitting. I posed the original question to Mr. Westfall about sealing on the 400/5.6L.




autochrome said:


> At the moment i have a 7D. I thought about a 2nd body, a 5D Mk.II, but resisted the temptation and invested in lenses instead. I'll skip the 5D Mk.II and get a 1D when the time is right.
> In fact i just got the 400mm, lack of full weather sealing and all. I thought the lack of IS would make it unusable (since it's a 640mm equivalent on APS-C), but it's not that bad. I'll just have to get some sort of weather protection when using it outdoors, other than this issue, my first impressions are positive. The 100-400mm was too cumbersome, i would be using it at 400mm mostly, and i got the 70-200mm range covered already. I'm not sure the 400mm f4.0 DO is fully weather sealed, but at the price Canon is charging for the DO you can make a bit of extra effort and go straight to the 500mm which is a far better investment (and would be even better if it included a chiropractor ).



Almost always good advice to invest in lenses more than bodies. The 400mm f/4 DO is fully weather-sealed, yes, but I agree - the reduced contrast with DO is a turn-off, especially in that price bracket. 

The 100-400mm is bulky, but one thing I like over the 400/5.6 is that the 100-400mm stores more compactly - I frequently go out with the 7D + 100-400mm in a Toploader Pro 75 AW and it's a perfect fit; the 400/5.6 is too long for that.


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