Well, I only have 9 on my T3i/600D . (and only the centre one is a cross type). But I seem to be able to get by, at least with the type of photography I do (landscapes, cityscapes, some wildlife).
More up-market cameras have a lot more AF points(eg the 7D has 19 points and the 5D Mk III has 61 points)
So my question is Ė when and how do you use all these extra points ?
My usual technique is to use manual AF point selection and always use the centre point. This means that I have to point the camera so that the centre point lies on the object I wish to use as my focus point, lock in the focus and then re-compose the shot. If Iím using a tripod, I might consider keeping the camera fixed and selecting an AF point other than the centre one but generally I donít bother. I suppose this might be a circumstance however where the larger number of AF points would be handy ?
If Iím using a tripod under low light conditions, more often than not I use manual focus. (Using the magnified Live View mode)
I never use automatic selection of the AF point as there is too much uncertainty with this for me.
I would be most interested to hear about the techniques that others use.