I use a Nikon D90 coupled with a 16-85 Nikkor lens fitted with a Nikon HB-39 lens hood. I have noticed when I use the camera in the upright position, if that is the corrct terminology, and use the built in flash, I get a small half round mark on the image, as is something is in the way, I am assuming it is the lens hood that is causing the problem as when I turn the camera around I get the same mark on the other side, and when I try with the hood off, it isn't there, so obviously that seems to be the problem. Anyone else noticed this, or is it just me? I could have understood it if I had been using a non-Nikon hood.