The AF-D type lens adds distance information to the data supplied by the lens to the camera and the AF-G type does not. The AF-G type removes the aperture ring, otherwise they are identical. The AF-D is an older model...both are sharp sharp sharp. Unfortunately neither of these lenses (60mm micro) will auto focus on cameras such as the D40, D60, D3000 which do not have the built in focus motor in the camera. The lens will mount and meter but has to be manually focused.