I am writing from personal experience. 50mm 1.4G AF-S + D3100 - terrible. The lens never focuses, it misses all the time. I took it to Nikon and asked to do the adjustment along with the camera. They said there were no problems with the lens, the camera did something in words. As a result, the photo session on the weekend was a complete failure. Unfortunately, the D3100 does not have autofocus adjustment, but nevertheless I am very disappointed. Money down the drain.