Quote Originally Posted by BetterSense View Post
Recently I have been trying to photograph a small round seed pod at about 1:1 with my Olympus OM1 and 50mm Macro with extension rings. I put the lens on f/22 which is probably an actual f/45 or so at 1:1. The 8x10 proofs I made aren't impressively sharp, and I think I have eliminated camera/subject motion as a cause.
I use a Nikon 55/3.5 at that ratio quite a bit, and keep the lens at f:4 which means f:8 working aperture. You're working at f:45, and diffraction is giving you mush. Your lens is limited to 33 lp/mm at that stop (assuming the film is recording everything the lens gives it), when you enlarge it to 8x10 that becomes about 4 lp/mm on the print.