MrFahrenheit wrote in post #13916409
It's obvious that you've done your research on this topic and understand exactly what the problem is. Don't second guess yourself too much on this, send the body and Canon lenses to Canon and have them calibrate the lenses to the body, then do the same with the sigma and tokina lenses.
I spent 3 months second guessing my results when I got my 17-55. I was easily able to get noticeably sharper images with my 50 1.8 on my 20D. I wish I hadn't spent so much time thinking that I should just enjoy the pictures and not 'pixel peep.' After I had Canon calibrate the 17-55 to my 20D, the difference was night and day.
Yes indeed! Agree completely! If your Canon warranties for the body and 50mm are current Canon have a responsibility that they are fit for purpose. With expensive complex precision gear that is factory manufactured, calibration of body + lenses is a normal and expected part of the selling-buying transaction. It is not something extra and optional you are asking for. Don't beg, insist, nicely. I don't expect that Canon will make any fuss at all. As for the other lenses, once you have your Canon items calibrated, and you test the 3rd party items again, if they are still in warranty and still don't perform, you have a similar right to approach the manufacturers.
Regarding MA, it is an extremely valuable tool, but mainly for primes. It doesn't much help solve fine focus problems with zooms. As others have remarked, there a number of factors that can cause fine focus problems, so even for primes MA might go a long way to remove gross focus problems but perhaps still not guarantee perfect focus.
AF itself is not a perfect tool, and focus errors will likely occur whenever it gets close to the limits of its comfort! The classic test situation you have described is in fact one which is very uncomfortable for typical AF - so many high contrast edges very close to each other in 3 dimensions! Yes, a good test, but too good a test for most AF! It could doom the AF to failure. Better I think to (also) test in a situation where the AF does NOT have any choice. If it fails there it does not have any excuse!
I had a quick look at this which I incidentally just found. Might be interesting?