I recently acquired a 500cm with WLF. It appears that I have the standard/stock screen installed. I am having one helluva time focusing. Using the magnifying glass, nothing every seems sharp/in focus. I have zero problems with either of my Rolleiflexes (1 ground glass, 1 Maxwell), rb67, m65, and c220 (all original screens). I do wear glasses, but I wear them with the other cameras and I'm fine with them. Is there a diopter in the 500cm I can change? I tried a Google search, but I came out empty handed.