Mark III AI Servo accuracy at slower FPS?

Rob Kircher

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As far as I can tell all the testing has been done at the advertised 10FPS. Has anyone tested at slower FPS? Say 8 or 5?

Yes I know this is not what Canon has advertised but I'm interested to see if FPS has an impact on focus accuracy? Is it possible that the focus engine can't keep up with the shutter speed? Is it possible that some of the photogs out there who are using the MIII have quietly slowed down the FPS to get expectable results?

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Rob Kircher
My Stuff: http://www.pbase.com/rkircher
 
Interesting post. This is because so many of us would love to see the 1D MkIII some understandable explanation for the focus issues. One that we could live with.

Regards,
Arcus
 
I don't think it does. I shot with it at 5 fps in Alaska, and on when ever i had contrasty backgrounds (water glare shooting whales or sea otters, or trees shooting perched eagles) I got all kinds of issues with center-point focusing oddities and oof shots)
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At the very begining, I found photography simple: Point the camera and push the button. After several weeks of practice, I discovered I could achieve even better results by turning the camera on and removing the lens cap.



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Makes no difference. I rarely shoot at 10fps, opting instead for 6 so i don't blow through too many frames, and i can say with certainty that i still have major AF issues. One way for any M3 owner to see this for themselves is to track an object and not fire off any frames. It becomes quite obvious that this camera will lose focus during tracking regardless of how many times the shutter opens.

The most frustrating AF issue for me has to be how this camera likes to wrongly shift focus after the mirror clicks up but before the shutter opens. I can be tracking a subject and everything looks perfect, i push the button, take the shot, and as soon as i can see my subject again, the camera has decided to mis-track and now my sub is OOF. This seems to happen A LOT, and it is always obvious when it does. I've blown so many shots this way and i'm becoming increasingly frustrated. To make matters worse, i've had my focus tracking set to slow because i thought i didn't want the camera shifting targets during tracking. This now appears to mess with the logic of the camera. If i'm tracking a subject and the AF shifts during a sequence to an OOF subject (which happens about 50-60% of the time), the AF now thinks it should continue tracking whatever it is that is OOF, and because i have it set to slow tracking, it won't recognize that it isn't in focus and will continue an OOF track! Does that make sense?

Yesterday i made 2 adjustments to CF3 which only slightly seemed to help: I went ahead and set my tracking to +1 so that the camera would check its AF more often and i set CF3-3 to #2 because i'm hoping that it will minimize the shift that occurs during a sequence. An odd sort of logic, but it seemed to help.

Really, all i want is for this camera to track the subject i assign, and to continue tracking that subject until i tell it not to. Why is this so difficult for the Canon engineers to implement?
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