Not sure I quite understand (sorry for hijack op), does this mean i'm doing it wrong?
In reality, if you are using a narrow aperture or your subject is some distance away, you are unlikely to see issues using by recomposing. The effect gets worse as you use a wider aperture and/or the subject is closer.
Also at particularly wide angles, the wide field of view means that the act of recomposing itself can move the subject much further away from the lens.
It's also worse if your subject is moving, as they are likely to have moved out of focus in the time it takes to recompose.
I often have to do some recomposition as the 60D has 9 focus points...
On a mostly unrelated note I was using the canon 50mm f/1.4 on saturday at wide apertures and selecting focus point on still subjects about 10-12m away, and not recomposing and was still getting shots out of focus. I'm not normally one to proclaim my lenses are back/front focussing but the actual focus seemed to be about a metre closer than the point I actually focussed on with everything else being still
, and no micro adjustment option on the 60D...
Unless you're shooting at f1.8 or faster on full frame it doesn't really matter too much because rarely do lenses have such dodgy planes of focus that it'll throw stuff out of focus. Basically the point is that lenses don't all have focus planes that run consistent to the field of view (so a lens might be focused at 2m in the centre of the frame but 2.03m in the corners) so if you focus and recompose there's no guarantee that what you originally focused on in the center is still in focus when you recompose and it's in the corner.
I think it is less to do with bad lenses and more to do with plane (ho ho) old physics. The plane of focus is just that.. a plane - so when you rotate the camera you are rotating the plane. When you recompose, the central point of that plane is still at the original distance, but that now needs to be moved closer to account for the fact that the plane on which the subject lies is now closer to the lens than it was before.
example of the plane of focus - but you have to use your imagination for the original plane of focus...
http://www.visual-vacations.com/Photography/focus-recompose_sucks.htm