i wear no. 2 readers. the perfect diopter for me is 0. the F-F2-FE2, etc., finders are -1. adding the 0 (actually a +1) brings the viewfinder to 0, or neutral, which is absolutely perfect for me. i learned this from Pickett Wilson here. Bessa R2-3-4 series bodies take nikon diopters, and 0 brings my R2m's viewfinder/rangefinder patch into perfection ...