Rob Galbraith comments on 1d3 AF

[X-Re]

I certainly cannot confirm or deny anything that Rob's documenting on his blog. At this point, with 2700-ish frames on it, my MkIII seems to do very well. Any files that were out of focus, I could immediately explain as user error (focus point slips off the subject during action shots, typically, which is definitely a "driver" problem). The camera focuses so much faster than my 30D, I'm not used to being as rigorous about keeping the area of desired focus under the AF Point.
 
In looking at Rob's examples, I wonder if this increased AF speed is what's getting him into trouble? The shot with the runner coming at him - her arms are periodically in front of her body and in the coverage of the AF point, and she is a low contrast target where the camera is trying to focus (the black shirt). It seems to me that this camera is fast enough to try to refocus on the moving arm as it crosses the body, potentially creating a front focus situation in relation to the face....

I've not shot much action with it, yet, so I definitely have not done an exhaustive test of the gear, but... mine seems to be pretty solid. 2500+ shots out of the first battery charge!

[jani]

In looking at Rob's examples, I wonder if this increased AF speed is what's getting him into trouble? The shot with the runner coming at him - her arms are periodically in front of her body and in the coverage of the AF point, and she is a low contrast target where the camera is trying to focus (the black shirt).

Galbraith has thought about the shirt:

As with other tests, we repeated several sequences with the athlete wearing a different shirt, to see if the camera's autofocus sensor was somehow reacting badly to a particular colour or pattern. From these tests and real-world shooting, we can see that whether the clothing is black, grey, white, blue, red, yellow, logo, no logo, it doesn't seem to matter: the autofocus problems are the same.

It seems to me that this camera is fast enough to try to refocus on the moving arm as it crosses the body, potentially creating a front focus situation in relation to the face....

Apparently, front focusing is not the problem:

Generally speaking, the camera tends to backfocus when it's focusing incorrectly.

Also, you should note that the problem appears when the subject is stationary, see the example with the goalkeeper (yellow shirt, number 1). You can't blame contrast, you can't blame arms or whatever moving in front of the shirt, and you certainly can't explain why the 1D MkII N performs far, far better under the same conditions.

However, if I (like you) switched from my 20D (you: 30D) to the MkIII, I'd still probably see a general improvement in autofocus speed and accuracy. But I've also seen the impressive performance of the MkII over the 20D, first hand.

[X-Re]

Also, you should note that the problem appears when the subject is stationary, see the example with the goalkeeper (yellow shirt, number 1). You can't blame contrast, you can't blame arms or whatever moving in front of the shirt, and you certainly can't explain why the 1D MkII N performs far, far better under the same conditions.

     I've been disregarding that test case - I have yet to handle a Canon camera that focuses reliably on static subjects when set to "AI Servo" (at least, when shooting hand held). My MkIII does it better than my 30D. I have not personally handled a 1DMkII or 1DMkIIn, so I have no experience with those.

However, if I (like you) switched from my 20D (you: 30D) to the MkIII, I'd still probably see a general improvement in autofocus speed and accuracy. But I've also seen the impressive performance of the MkII over the 20D, first hand.
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      I agree - this is not my first experience w/ Canon's pro-level autofocus systems, though. I used an EOS-3 for a long time. Same/similar issues there, as well. With no personal experience with what appears to be considered the "golden" platform (the 1DMkIIn), all I can say is that my MkIII exhibits roughly the same behavior as every Canon camera I've used (and, interestingly, the D2X I've used, as well, for the most part - not exhaustively tested, though) - the MkIII is just faster about it.

      If Canon can make it better, heck, I'm all for it.

[jani]

I've been disregarding that test case - I have yet to handle a Canon camera that focuses reliably on static subjects when set to "AI Servo" (at least, when shooting hand held). My MkIII does it better than my 30D. I have not personally handled a 1DMkII or 1DMkIIn, so I have no experience with those.

According to Galbraith, the problem is not limited to AI Servo:

Focus can shift slightly but constantly at times when the subject isn't moving. Under certain conditions, the subject may not actually come into focus through a sequence of frames, even though the point of focus can be seen to be shifting throughout the sequence. This is true whether the camera is set to AI Servo and focus is active throughout the sequence, or when it's set to One Shot and focus is activated between each frame.

      I agree - this is not my first experience w/ Canon's pro-level autofocus systems, though. I used an EOS-3 for a long time. Same/similar issues there, as well. With no personal experience with what appears to be considered the "golden" platform (the 1DMkIIn), all I can say is that my MkIII exhibits roughly the same behavior as every Canon camera I've used (and, interestingly, the D2X I've used, as well, for the most part - not exhaustively tested, though) - the MkIII is just faster about it.

      If Canon can make it better, heck, I'm all for it.

If we are to believe Rob Galbraith, Canon made it better in the previous model, 1D MkII (N).

Keep in mind the shooting conditions where the problems occur; the camera appears to handle autofocus superbly in other conditions.

The weirdness is that this happens under sunny and warm conditions, exactly the kind of conditions where one would expect autofocus to behave normally.

[MarkKay]

RG updated his article today July 2 and it is not pretty.  Basically still many AF issues that are not solved by different CF parameter changes and with a 3rd production camera.

According to Galbraith, the problem is not limited to AI Servo:
If we are to believe Rob Galbraith, Canon made it better in the previous model, 1D MkII (N).

Keep in mind the shooting conditions where the problems occur; the camera appears to handle autofocus superbly in other conditions.

The weirdness is that this happens under sunny and warm conditions, exactly the kind of conditions where one would expect autofocus to behave normally.
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