I have used the Tokina 12-24/4 with my D200 for many years. It is an excellent lens, and I never had a problem with it. I don't think that a UV filter serves any useful purpose. In fact, some of the "vignetting" in #1 is apparently caused by the filter. Regarding the over exposure in #2, I have no explanation. Perhaps the exposure compensation was set incorrectly, or the picture was part of a bracketing sequence.