In the case of the Bessas, the R3-a has a 1:1. This means that you can't get a 35mm frameline. You get the 40mm instead. This could mean a lot if you own a 35mm lens(es) or it could mean nothing.

As to aperture, ummm....f2.8 is f2.8.


F stop numbers are ratios, so they are the same on all lenses. F8 is f8 no matter what.