Using AutoFocus. I believe this camera is back focusing, particularly in shutter priority/sports shots. I am using a 70-200mm VR f/2.8 lens. Object that was focused on is blurred, but background is sharp. I put the same lens on my D200 and shot the same subjects, same time of day, same priority. Shots of the subjects are tac sharp. I also tried the same combinations on bird shots. All the D300 shots are blurred. None of the D200 shots are blurred. I have also noted when using a 300mm f/4 that objects to the side of the subject may be sharp, while the subject is partially blurred. So it is not the lens I don't think, but the camera itself. Is this a problem that is fixed at Nikon Repair Center??? I love this camera, when it works right, but I sure have been doing a lot of photoshop sharpening with it. Do not have those problems with my D70 or D200.