I think I am going to do a test. A bit like the Leica test, but maybe 12 pins one inch apart. I can focus on the central one (say pin 5 or 6) from distances of 3 feet, 5 feet, 10 feet, 15 feet, and expose at full aperture for whatever lens I am using. I'll use b&w film, maybe ultrafine Xtreme 100ASA of Polypan F. I can do the test in the alternative, focusing using the split screen, where the camera has one , and the ground glass. I will do this for each of the cameras I use regularly. Give me a week or so to get through this all and I will report my findings.

My eyes are not what they used to be, but are pretty good with glasses. I usually use my glasses when focusing, except in the case of one of the Nikons that has a corrected viewfinder that seems to suit me.