Hello, I just bought my wife a pristine-condition Nikon F3 with a 50mm f1.4 AI-S lens from a reputable dealer. Having put three rolls through the camera now it's clear that it is suffering from backfocus. At f1.4 the focus consistently comes out 5cm or so in front of where it's intended, and there are similar errors at smaller apertures. It focuses fine at f11 and beyond. The lens functions perfectly as I've tested it in precisely the same conditions on my D850. I'm about to take it back to the dealer for, I assume, adjustment, but before I do: Has anyone else experienced this problem, and what can the cause be? I don't quite understand how the image can be perfectly in focus in the finder, and accurate according to the distance scale on the lens, but still out of focus once it hits the film plane. Any explanations gratefully received, thanks!
