focus issues

[Hdub]

I've been taking photos of high school football and more often than not my main subject is slightly out of focus. I've tried using different focal point settings but it still happens. I have also tried diffenent ISO, shutter speeds. Aperature is set at 2.8.
I use and xti and 70-200L IS.
Is it a lack of experience? Any comments and suggestions appreciated.

[Gatorboy]

If you shooting action, you better make sure your camera is in AI-Servo mode.

[Hdub]

Yes it is, thank you.

[WaltA]

I've seen a few other threads similar to this and it seems the consensus seems to be that the AF is actually focusing on a different subject than you want it to. Maybe the background or another player.

If you do a forum search for "AF" or "focus" you find some of them. In some cases the images posted show the Focus Points and you can see in most cases why the AF didn't work the way expected.

I'm just starting to work through some of the same things with my Xti (learning the AF points and changing them manually) and I'm sure there will be some more posts in response to your question.

[Rmclain3]

I just sent my XTi and 70-200mm L IS USM back to Canon for focus issues. SInce I wasn't sure if it was a lens or camera issue, it was suggested that I send both back for evaluation. They told me on the phone that it was probably a camera issue, not lens.

Man I'm worried about this..................

[sldghamr]

My XTi just came back from Canon Factory Service for the FOURTH time for consistent back focus behavior. In my opinion, and from my experience thus far there appears to be a fundamental flaw with the design of the AF on this cam. I have a Sigma f2.8 18-50 and EF 70-200L f4 and they both do it. The last 2 times back to service I've included the L series lens as I did not buy the kit lens (so the EF is the only Canon lens I have.) On a tripod, with wireless remote control, manual focus point selected (center), it's back focused, every blasted time. And the more distant the subject, the grosser the focus error. The last time I sent it in I requested that they replace both pieces since they failed to get it right after three times, what good is a fourth trip going to do? Insanity anyone? They ignored me, shipped me my original items back and still failed to fix the problem.

I'm not impressed with Nikon, they feel (and sound) like toys, but at this point Canon is worse - because if there is a problem, they can't get the job done and you're stuck with garbage. This is my fourth digicam, I'm not a newbie so no flames please from the SLR snobs out there.