Michael Ging , Jan 27, 2011; 12:18 p.m.
THe DOF on this lens is measured in millimeters when you are shooting at F2 or 2.8 and close focus, so make sure its focused on exactly what you want to be sharp. Putting a camera on a tripod might keep the camera still for low light shots, but if you are photographing a living being, or something that can move, you might have subject movement. Are you sharpening the photos in a processing program like Photo shop? If not then you will never see true sharpness. If you can post a photo , it will help us find the problem.