Oh, I forgot to mention... Here's something important to know about buying diopters for the r2s. They take the FM10 diopter. Now Nikon's viewfinder is built at -1 and the diopters that they sell for them are rated at the FINAL diopter value, (not the value that the diopter actually is!)
So, for instance, I need a -1 diopter to see. (-1 is what my glasses are rated.) Since the Nikon viewfinder is normally -1, they don't sell any that read as -1. (Because you would never need one if you have an FM10, you're already at -1.) The r2 viewfinder is set to neutral, so what I needed to get was a -2 (which is actually a -1.)
Confused? It took me a while to figure this out since no one explained it to me. Anyway, all you have to know is that when buying FM10 diopters for the bessa r2, they are all rated 1 diopter value higher than they should be. So -2 is actually -1, -3 is really -2, 0 is +1, etc. If, of course, you're buying a diopter for an FM10, then you should just get the rating that you need and you'll be all set.
hope this helps.
adam