The saga continues. My modification of the t-mount shouldn't have had any effect on the focus, because I only removed material from the circumference of the threaded insert. Both the Petri and Nikon adapters measure the same thickness, although the Petri bayonet and Nikon bayonet mounts are different. So I dusted off my old Nikon D200 and put the lens on it, and seemed to focus the infinity OK. (at least as OK that manual focussing a digital camera gets) The digital confirmation light lit up, so I took a few shots and put them on the computer and everything looked in focus. I upped the ISO so that I could use a high enough shutter speed for the lens to be set wide open. (5.6 @ 500th sec.) Took a couple of shots at an object about 100 to 150 ft. away at both 100mm and 200mm, and it looked sharp at infinity. Now I'll admit that the difference between a FTN and a D200 is fairly large, but I can't believe the lens mount and film plane/sensor plane is different, or you wouldn't be able to use any Nikon film lenses on the digital cameras. Maybe I'm wrong, and this is some more digital voodoo stuff. Any thoughts on this?