Jai long hesitated between the Sigma and Nikon 1.4D, G for me being off budget. After spending several days on the internet to read various comments of users, I have realized that some copies had big problems dautofocus, i still gave it a shot and I have absolutely no regrets. Mounted on my D3 it really works well. Color contrast, sharpness, brightness, speed is everything .... it is good at 1.4 and 1.8 from this is the top .... Super optical Sigma.