I just noticed that when I look into the viewfinder of my F6, on the bottom part of the screen, there seems to be 2 areas that appear color distorted. It is somewhat like a faint rainbow, like oil on metal with different shades present. I don't know if I can describe it anymore accurately. Has anyone noticed this in their viewfinder, F6 or other recent Nikon SLR? The mirror is absolutely clean.