40D Autofocus problem

Started Apr 19, 2012 | Discussions thread
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denzelnukes
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40D Autofocus problem
Apr 19, 2012

I need some help with a friend's 40D that is having an autofocus problem. Hopefully, this isn't too sketchy. I've had a T2i for a short while and I'm not at all familiar with the 40D. And I don't have the camera with me right now so I have to go by memory.

Here is what I could recreate (with half-presses of the shutter button). In the auto setting with her lens (28? 35? to 135? zoom, USM), it would autofocus correctly in relatively close shots (5 to 10 feet). Then, when I would point the camera at the house across the street (about 100 feet) the focus would adjust a couple of times in one direction only then stop trying, leaving the scene out of focus. I'm not sure what would make the camera start responding again, possibly turning it off and on again (I tried several things and I don't remember what consistently worked). I could recreate this problem with the lens IS on and with it off.

Then I switched lens to the one that originally came with my T2i (18-55mm) and I could once again recreate this problem. Which would lead me to believe this is camera related.

Also, I noticed the following behavior while autofocus was working. When I autofocused with half-presses on a scene that was relatively close (I think this also was true of further away scenes when autofocus would work) without moving the camera, the autofocus points would light up differently each half-press. And it would always be 1 or 2 points, never more than 2 and never be the center point. So, I'm thinking there is also a setting for autofocus that is not set correctly. I've downloaded the manual to look at it today but I had no idea on how to change this when I had the camera last night. But I'm also thinking that no matter what the autofocus setting, it shouldn't exhibit the behavior I described above. At least one point on the scene should be in focus.

Thanks for any help or insight. You guys have always been helpful.

Canon EOS 40D Canon EOS 550D (EOS Rebel T2i / EOS Kiss X4)
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