Seeking the lens market AND the related info WRT Canon 1D X, I found some things which seems concerning:

1st, a note from Canon's Chuck Westerfall (see here) saying:

“AF is unavailable on the EOS-1D X if the maximum aperture reported to the camera through the electronic lens mount is smaller than f/5.6. This is a lower specification than previous EOS-1 series DSLRs. [...]"

On the article linked above, it is stated that no lens have f/8 but it can be reached by using teleconverters. Ok, so far, so good.

...But having in mind the above, this means that the new Canon 1D X cannot focus on the longer (telephoto) lenses which have an aperture smaller than f/5.6, say 6.3?

This includes (at least) the following lenses:

From Sigma:

  • 50-500mm F4-6.3 EX DG HSM
  • 150-500mm F5-6.3 APO DG OS HSM
  • 50-500mm F4.5-6.3 APO DG OS HSM
  • 28-300mm F3.5-6.3 DG Macro

From Tamron:

  • 28-300mm VC F/3.5-6.3 XR Di VC LD Aspherical [IF] MACRO
  • 28-300mm VC F/3.5-6.3 XR Di LD Aspherical [IF] MACRO
  • SP 200-500mm F/5-6.3 Di LD [IF]

...so, by buying Canon 1D X and having at least one of the above lenses and raking out the glass, one cannot use the AF anymore?

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    Hmmm. I'm not sure I see a real question here. If you have one of those lenses, and it is important to you, and you can't replace it with something else, and you were planning to buy this top-of-the-line camera, you have a problem you need to resolve by changing one of those assumptions. That might be painful, but is not really in question. Otherwise, there is no issue, and again this would be a complaint but not really a question. – Please Read My Profile Nov 5 '11 at 16:30
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    Maybe a rewording to something like "Is AF a f8 useful for professionals or a gimick to make the specs better?" as I can't see many professionals having the slower lenses and it's more to lure people like me in who wish my 70-200 f4 L could auto focus if I got a 2x converter – Dreamager Nov 5 '11 at 16:43
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    Are there any questions/resources that would explain WHY they would do this? I've never heard of this. – Vian Esterhuizen Dec 9 '11 at 22:31
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    I think the real issue with this limitation on the 1D X is lenses combined with TC's. Take an f/4 telephoto lens and slap on a 2x TC, your screwed. A LOT of wildlife, sports, and race photographers (and probably air show photogs) tack on a TC or two extend their reach. Being able to center-point AF at f/8 is incredibly useful for that purpose, and losing that capability is really going to limit a LOT of people. The best backup options, say the 600mm and 800mm f/5.6 lenses, cost an arm, leg, kidney, and firstborn too, making owning an alternative difficult for many. – jrista Dec 10 '11 at 5:08
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    Canon recently released firmware v1.1.1 for the Canon 1D X. This firmware enables cross-type f/8 AF with the center point, including in AF Expansion mode, which also enables the surrounding four points (above/below, left/right) in either horizontal or vertical mode. That allows a total of 5 AF points to be involved in f/8 AF with the 1D X now. – jrista Oct 19 '12 at 15:27

Sigma 28-300mm F3.5-6.3 DG Macro? You are going to get a $7,000 camera with that piece of glass? Or even any of those Tamron's. I highly doubt anyone in the market for the 1DX even has these in a backup kit.

How important is it? Not important at all.

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    I agree. The lenses listed here are consumer grade lenses, I can't imagine that Canon would even pause for concern about them. – John Cavan Nov 5 '11 at 17:32
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    Agree, most folks needing a camera in this class also use 400 f2.8, 500 f4, etc lenses. – cmason Nov 5 '11 at 23:32
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    I agree. Their backup kit would be like 5D Mark II or a Leica M9 etc and nothing from Tamron. – Gapton Nov 8 '11 at 14:24

No non 1-series Canon DSLR advertises AF at f/8. However, it's not the case that AF wont work at f/8, just that just that f/8 is beyond the design parameters set out when the AF unit was designed, thus it's not guaranteed to work at this max aperture and Canon quite reasonably disable it to prevent any problems with AF performance biting them (and to help sell faster lesnes ;)

There's a well known trick whereby you tape the pins on your teleconverter to prevent it from reporting the true aperture of the lens+converter combo so that AF remains enabled. In a very similar way the lenses you listed simply lie to the camera so that AF remains enabled. And f/6.3 is not that much past f/5.6 so it works reasonably well.

All the lenses you list will AF at the long end on current Canon non-pro bodies so will work exactly the same on the 1Dx. Or to echo dpollitt's summary above:

How important is it? Not important at all.

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  • Canon apparently turned AF totally off on the 1D X via firmware if the lens didn't report an aperture of f/5.6 or wider. This was unlike the Rebels, x0D, 5D, and 7D line that would continue to hunt when the max aperture was narrower than the rated f/5.6. They heard from plenty of 1D mkIV and 1Ds mkIII users who were thinking about upgrading to either a Nikon D800 or D4 instead of the 1D X. Canon saw the light and issued a firmware update that enables AF to f/8. They also announced a similar firmware upgrade for the 5D mkIII due early in 2013. – Michael C Feb 7 '13 at 16:44
  • Canon discovered many of the buyers of their extenders were not, as they had assumed, using extenders instead of super telephoto lenses, but rather they were using them with them. This included some of their high profile users such as Art Wolfe and other top professionals in the sports and wildlife segments. – Michael C Feb 7 '13 at 16:50

I find the limitation of the 1DX to focus only for lenses with apertures less than 5.6 to be a major deficiency. I probably would not have bought the 1DX if I had done my homework beforehand. I have several lenses, including the canon 100 - 400 mm and the canon 800 mm lens which will not AF with a 1.4X extender, so I'll still need to carry my 1DMKIV for those long shots.

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    What is your opinion of the 1D X now that they have issued a firmware update to enable AF through f/8? Is AF usable with the 800mm + 1.4X extender? – Michael C Feb 7 '13 at 17:09

Combined with the fact that there's no more 1.3x crop factor as there was in previous generations of 1D, it will be a problem for some wildlife photographers shooting already with f/5.6 lenses or f/4 combined with teleconverters (e.g. any Canon lens longer than 400mm, or Sigma 300-800 f/5.6) - adding tele conversion to make up for the lost crop factor would push those lenses over f/5.6. They can either stay with 1DmkIV, use a third-party TC or downgrade to 7D which would give a little tighter angle of view, albeit with worse low-light abilities. If they were shooting f/4 with 2xTC or f/5.6 with any TC, 7D would only help them if they reduce/lose the TC.

So yes, it will matter to some people, but probably not because of the lenses mentioned in the question. Some of those lenses, like Sigma 50-500, have been reported to be lying to camera about their maximum aperture in long end to get the Canon bodies attempt AF.

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    except serious customers who are the intended buyers for the camera will not buy the lenses you mention, they'll be using f/2.8 zooms and especially primes almost exclusively, unless those simply don't exist for the focal length. They're also not afraid of manual focus, and often will prefer it for situations requiring such long focal lengths. – jwenting Nov 7 '11 at 6:55
  • Yes, I can't think of a small aperture AF lens sold in the EOS mount that doesn't fudge it's way around the f/5.6 requirement. They'll autofocus, just don't expect them to perform as quickly or as well in low light. – AndrewStevens Dec 9 '11 at 22:48
  • @jwenting: Many of the longer super telephoto lenses used by the top sports and wildlife photographers are f/4 and f/5.6. Canon assumed most buyers of their extenders were using them instead of super telephoto lenses. What they heard from some of their most valuable and high profile customers is that they are using extenders with the super telephoto lenses. Can you imagine the waves it would have created if someone like Art Wolfe or Peter Reed Miller had jumped ship to Nikon? – Michael C Feb 7 '13 at 17:06

This is no longer the case. Canon just announced a firmware update that will enable AF at f/8 using the center point.


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As all Canon lenses for which it is designed will work fine, the niggle is about other manufacturer's lenses, and perversely wanting to "see through a glass, as it were, darkly".F5.6 is already very slow. Its virtue in a lens is its far greater depth of field, such that if a machine can autofocus accurately at f/5.6 then more of the image will be sharp than at f/2 or f/2.8. Given enough light there is no advantage in using bug heavy expensive lenses, and canon has a whole range of good slower lenses. We just must pray that noise is at least as unobtrusive at high ISOs as a Nikon D700, for which you can buy cheap Nikkors and just ramp up the ISO.

As a 1Ds MkII devotee (the best DSLR ever made?) unless I am going into video bigtime there is no advantage in slightly increased resolution of a 1D-X, but boy, I want one because I am sure its autofocus will better than my machine and hopefully it will accurately render all colours, and by this I do mean red, red red, and blue. I just hope you do not have to see AF points onscreen all the time, as slower lenses greatly emphasise their presence. Slow lenses are good on high quality sensors, but as Canon rightly realised f/6.3 is too dark.

You can of course go out and buy focussing screens from Canon that are designed for manual focus, but f/6.3 is still too dark.

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