I currently own an EL2 and a FE2 and they now both have genuine Nikon FM3a +0 diopters. However, I recently noticed that my eyes does not like the eyepiece very much. I have examined my medical records, and played with my Pentax LX which has a finder that includes built-in diopters, and determined that my best option would be a -1 diopter. I have checked with B&H and they only have -2 diopter from Nikon, but they do have -1 diopter for the Zeiss Ikon, which AFAIK is the same as the Cosina Voigtlander Bessas. I have read somewhere that Bessas can take Nikon diopters, so I wonder if I can use these Bessa diopters on my Nikon cameras too. It seems that the Bessa ones are slightly larger, so I don't know if it would protrude anything.