I just bought this brand new lens, and I am not sure if I have a lens problem or a camera problem. I have two cameras in question, a F601 and a D200. It works flawlessly on the D200, but who cares... On the F601, it focuses fine. The stops all appear correctly in the display. The film constantly comes out way over exposed. I put the F601 in manual - speed Bulb. I bring the stop down to 1.8 and look through the camera. The iris appears completely open. I stop down to 22 and the iris looks as closed as it should. I have had this F601 for years and works fine for all my other lens. Any ideas?