Autofocus problem

I have a Rebel XT with the 18-55 kit lens. Lately I've been noticing more and more that when I try to take a picture that when I press the shutter 1/2 way the little red dots appear in all the squares in the viewfinder. It used to be pretty good with 'knowing' what I was wanting to focus on but now it just tries to focus on everything. So more and more I'm having to push the button that lets me manually control where I want it to focus. Anyone else having this issue?

Your camera can never "know" what it is that you want to focus on. It's going to pick the spot that has the most contrast, and that may not be what you want as the point of focus in your image. You need to take control of your cameras focus and choose the active focus point yourself.

Mark

I know that it doesn't know. For instance though, in the past say if I was close to a big tree that I put on one side of the frame and there is a lot of depth behind it. In the past it would almost always focus on the tree and only that square would light up. Now they all do and I would need to select manually for the tree.

It could be your AF focus mirrors are misaligned. The only way to know is to send it to Canon. Not many here let the camera choose the focus points. Most of us prefer to choose it ourselves.

Mark

I always manually select the AF point, unless im tracking moving objects.

My Camera Had Autofocus problems. Turns out, that against my previous knowledge, most of the sensors are not located on the actual mirror, but in the Sub-mirror, a smaller mirror behind the big one, that actually blocks the direct path of the shutter. My problem was focusing period. It would hunt to infinity on a lens, and then come all the way back (in USM, so pretty fast) to zero, to let me know it could not focus.
When it went back to Canon Repair Service, I spoke to the Pro Team there, and he explained that there are extremely tight specs -duh- for that submirror, that moves just as much as the real mirror does. They replaced the entire assembly, and it worked.

That is my experience.

I would suggest - for the sake of troubleshooting - that you switch the AF mode to manual, and that you then select the center point, and continue to test it. If AF works in one mode and not the other, then you have a situation you may cope with, realizing the focusing is somewhat impaired (as said above probly misaligned) and other AF points are more effective than others. Or, you may also notice the AF is pretty weak at its strongest point (dead center, single sensor). Then you can evaluate options for repair. The Replacement on a 1D Camera costed me about $195 less than a month ago.

Best of Luck,

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