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Assuming I'm using center point AF. When I half-press the shutter button to get the subject in-focus, I believe the corresponding exposure value is also locked by the camera's metering system. Now, as I shift the camera to recompose, the final exposure value might be different from what the camera has locked. Will this cause a problem to the resulting image (incorrect exposure)? Are there better alternatives to this commonly used technique?
Most SLR cameras allow you to set the focusing and metering points so that they are not at the same location. It varies depending on the camera maker, but with Canon cameras this can be customized using the custom functions menu. I've used it a few times where I first set the focus lock, then the exposure lock (using the * button if I recall). If you find that this technique is difficult, you could also try using an exposure compensation (if you happen to know what the exposure ought to be).
Another drawback of focus/recompose worth considering is that for close subjects with shallow depth of field (such as many portraits), this will cause your image to be front-focused on the subject. Sometimes it's worth using an off-center autofocus point so that you do not have to recompose.
The * button as McQ mentioned can be set to become "the focus" button on my EOS as well. However, I don't use it. Also, I never got in the habit of using exposure compensation since I resort to manual when needed.
I typically shoot in manual exposure and just ignore the false exposure meter signs the camera gives me as I shift the camera (since I know the exposure is right when I set it before moving the camera).
As McQ mentioned, in some situations, especially at wide open apertures, center focusing then switching might cause back/front focusing. I don't think this effects every shot, but for those critical ones, I try to use of center focus points. Switching focus points on the my camera (Rebel XTi) is very easy and can be observed in the viewfinder.
Yep, using a peripheral focus point is the best solution, I think...