How accurate should one expect autofocus to be?

Started Mar 30, 2013 | Questions thread
SixtenB
New MemberPosts: 6
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Re: Do you know what contrast AF really means?
In reply to Just a Photographer, Mar 30, 2013

Just a Photographer wrote:

If your 2 year old is physically moving (eg. moving his/hear head) all the time, your camera will continuously detect different contrasts. So at times your camera might see the biggest contrast in e.g.. hair/ear or head/background instead of the eye you thought you were focusing upon. This does not mean your camera is faulty, but it just selects the AF points that has the biggest difference in contrast at the moment you press the shutter.

This can be any of those 9 AF points that are active as you have set your camera to allow it to do this. I would therefore advise you to set AF-S or AF-C 1-point as default and first try if this solves your problem.

Thanks, I tried AF-C single point, and that seems to give much more consistent results. From the manual, I had assumed that the d9 mode would initially lock focus on what is behind the selected focus point, then keep tracking that object as it moves under all 9 points. From your and tiko's posts, it sounds like it is much less sophisticated than that.

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