I'm a primary Canon user. I owned before the canon 50 mm 1.4, a trully excellent lens for the money too. But not to sharp wide open. You have to stop down at least to f2 in order to get good contrast and saturation. Also, the focusing ring was bad in my opinion. In the other hand, the 50L 1.2 was a big dissapointment to me.I expected the same image quality as the 35L or the 85L for that price. When I received the Sigma lens I really love it at once. The construction was amazing, solid as a tank, and the ring is very smooth. What have really impressed me was the performance wide open. Images are clear as crystal with good color and rendition. Fully recomended.