Dlee13 wrote in post #16857357
A few reviews have already stated the Sigma 50 art has AF inconsistencies so I definitely wouldn't upgrade, I plan to wait as well till Canon upgrade their 50 1.4.
I have seen some of those reviews mentioning AF inconsistencies. One very extensive review, where inconsistencies were observed, summarizes the lens with the following comment:
The market is full of 50-something mm lenses as seen listed in the comparison tables above, but there are significant drawbacks to all of them with wide open image quality being the primary issue. As long as the price is not objectionable, the Sigma 50mm f/1.4 DG HSM Art Lens is my strong recommendation over all of them with possible exception for the last 50mm lens to hit the streets with great acclaim, the instantly-legendary Zeiss Otus 55mm f/1.4 Distagon Lens.
My own experience with the Sigma 17-70mm f/2.8-4 lens was very positive. I purchased the lens at a local "store" event that was attended by a Sigma representative. My PC at the time was running Windows XP which is incompatible with the dock software. The Sigma rep took my purchase and 60D body and on the spot tweaked the combination for me. It took about 20 minutes and therein may be part of the issue with dock compatible lenses. It definitely take some patience and I think some people all too often give up and then blame the lens as inconsistent.