I have a Fuji 400-T lens I bought from Midwest last fall. I'm only saying where I bought it to indicate that it should be functioning well, since Midwest is such a reputable dealer. On at least two occasions where I've tried to use it near the limits of its coverage, I have composed with the lens wide open, and then I see some serious--no, HUGE--vignetting when I stop down. It's as if the lens' image circle is being cut in half or something when I stop down to about f22 or further. Can anyone explain what's going on here? Is it something in the design of a telephoto? Do I have a lemon? I should probably stipulate that, at least as I recall, the vignetting occurred at the bottom of the ground glass, and occurred in situations where I used a combination of front tilt and rise. I know that there are issues with tilt in telephoto lenses, but I've never seen anything about this sort of problem. Thanks for any help.