Quote Originally Posted by ntenny View Post
No, I think I'm not misunderstanding something, then. If the Xenar is diffraction-limited at f/8-f/11, and 1500/f is a decent rule of thumb, then that means that the lens resolves circa 150 lpmm, right? Which sounds kind of high, certainly much finer than most films could resolve.

136 lp/mm, actually.
Did you read the part where I said I'd "hazard a guess"? That's what I did, and I've used enough of those lenses on Rolleis to know that they will outresolve some films - for instance Kodachrome PKR 64. 136 lp/mm is not unreasonable for a high quality 75mm lens designed for that format.