Re: Sigma 70mm f/2.8 macro
I have this lens also, and have no problems on both my t2i and 5DM3 with viewfinder autofocus - it's right on, with no AFMA needed. It is a little noisy focusing compared to my other lenses, but the image quality is outstanding - probably the sharpest lens I own. It does, however, have problems with LiveView autofocus for some reason on the 5DM3, but not on the t2i. I have the same issue with my Sigma 150 macro - great image quality, no problems with viewfinder AF, but hunts and sometimes misses with Liveview AF.