I recently disassembled an Edixa SLR to reglue a shutter strap that came loose. This required removing the mirror box and consequentially the lens mount from the camera body. The mount had a number of shims behind it to align it properly with the film plane. I want to know what the proper procedure is for checking the alignment of the mount with the film plane. I assume this is something that cannot be done by simply checking focus at the film plane with piece of ground glass, or can it? I doubt one could see a tiny amount of misalignment this way.