Auto focus above f/5.6 with 5d Mark III?

[kpe_slotkin]

<p>One of the advantages of the 1 series over the 5 series was the 1 series ability to autofocus beyond f/5.6. Now that the 1DX and the 5D Mark III seem to have the same focusing system, will the 5D Mark III be able to autofocus past f/5.6?</p>

[zml]

<p>1Dx and 5D3 don't have the same AF system but neither will focus above f/5.6 regardless.</p>

[bobatkins]

<p>Michael is correct about AF operation. Neither the 1D-X nor the 5D MKIII will AF at f8.</p>

<p>The 1D-X and the 5D MkIII do have the same AF sensor <strong>hardware</strong>. However the 1D-X has an additional processor and (I assume) different firmware. </p>

<p>Based on feedback from users I understand that Canon USA have made Canon Japan aware of the issue, but what that means (if anything) I don't know.</p>

<p>My understanding of the issue is that Canon had a choice of either better overall AF performance at f5.6 and faster by designing the AF system for that, or designing it for f8 operation and losing some overall AF performance. They chose the later over the former.</p>

<p>There has been talk on forums (uninformed speculation) that perhaps Canon might issue a firmware update to allow AF at f8. However the AF ability is based on the hardware as well as the software, so I'm not sure how likely (or possible) this would be. Both cameras could certainly be allowed to try to AF at f8 with a suitable firmware change - and under good conditions they could both do it - but I'm not sure that Canon would officially support an AF operation that couldn't fully meet their specs for AF.</p>

[keith reeder]

<p>http://www.photo.net/canon-eos-digital-camera-forum/00aC1T</p>

[zml]

<p>The didcated AF processor, and associated firmware/software, seems to be a rather critical part of the 1Dx AF subsystem so these subsystems are different on the cameras in question. As for the identcal hardware, other than a dedicated AF processor on 1Dx, I don't know. The 5D3 and 1Dx have the same number of focus points and seem to have a rather identical quoted focusing sensitivity, but whether the physical beam splitters, focusing screens, etc. are also identical, it is a big fat enigma at this point. And although I did lovingly fondle the 1Dx twice, I have no idea what's inside and how it might perform.</p>

[cmitchell]

<p>Please humor my question because I never heard of a camera that wouldn't auto focus over f/5.6. My 7D auto focuses all the way to f/22. You're saying that this camera needs manual focus after f/5.6? What is the reason for that?</p>

[bert_pohl]

<p>Hi Christine,<br /> Yes indeed, lenses can focus for pictures taken at their narrowest f-stop... But the way they to it is by focusing at a wider f-stop & the aperture stops down when the picture is taken...<br /> Which is all to say that the problem occurs when you slap a lens on the camera body that is physically unable to open up wider than f-8. Given that the camera can't "cheat" & gain the depth of field it needs, the focus sensors are unable to obtain focus...<br /> Hope that helps a bit. The opposite also holds true for f2.8 lens. In this case, the camera appreciates the wider f-stop and will obtain faster & more accurate focus than if the lens was only f4.0 (at least that holds true for the main focus points on pro/semi-pro camera bodies) :-)</p>