I've been using my Nikon 18-200 (on my D300S) for a few years now and the only problem I've ever had with it is some heavy vignetting at maximum zoom. Today I had it out and have a problem at the other end, 18mm, the large dark blotch at the top centre of the photo (see attached). I've used this lens on this camera in this kind of lighting many times before and at similar settings (using aperture mode) and never experience this before. I wanted to set up for a bracket set and then I discovered what might have been my problem: I thought the aperture setting was at 5.6 (and it was when I started out) but I noticed it had somehow been changed to f22 (and 1/40). Could the small aperture and wide angle result in what I've described above?