I had previously experimented with tamrons that had focal lengths that were comparable to this Sigma. Everyone had things they could improve on, but unfortunately there was no money for this lens. The presence of a Canon 50mm f/1.4 lens was the only thing that was pleasing to the eye. This lens worked quickly, hit its target accurately, and produced an excellent picture that was very sharp. I made a decision, and I sold all of the lenses simultaneously. This one had to wait for three weeks (they ended abruptly in all warehouses). After what seemed like an eternity, he arrived, and the first thing that struck me was how big and heavy he was considering the distance between us. My wife is unable to carry the 50D now that it comes with its battery pack, flash, and this lens because it is too heavy. Assess how well the stabilizer works at low shutter speeds and the 55th end of the exposure range using the first few frames. It is not possible to make a comparison between the speed of focusing and that of an ultrasonic sigma motor or even a regular tamron motor. When compared to sigmas and tamrons, the number of focusing errors is drastically reduced. The 2.8th hole is coming along nicely. This lens didn't even need to be aligned by me (although there is an in-camera adjustment in the carcass). In general, I am not unhappy with the lens, and I believe that it is definitely the best option for crop. The sharpness is comparable to that of a 50mm 1.4 lens. If there are ways and means to move it, then you should do it without hesitation because it is sufficient for the vast majority of scenes, ranging from landscapes to portraits.