I need help diagnosing a problem I have been having lately with my Nikon F3. I took this camera to a Unique Photo store and stumped all four guys who came to help. As you can see in the attached photo, an inconsistent black shadow is appearing in some of my exposures. I have ruled out the camera strap, and after examination, the shutter does not "stick". This happens without flash, and does happen with multiple lenses. Help! I don't want to risk ruining any more photos. Any ideas?