Bought this lens off another site. I'm professional jewellery/portrait photographer and this lens by far exceeds all expectation. Tack sharp pictures even in low light, absolutely to chromatic aberrations or vignetting! Sharpness is maintained right from f2.8 till f16 and then it starts dropping slightly. Built like a tank but auto focus works like hot knife on butter, smooth and silent. Full time manual focus is of great advantage while shooting in low light.