I'm wanting to get a 35mm rangefinder and for my budget it looks like it'll have to be one of the Bessas. I see there are a variety of these, R2, R3 and R4, with an A or an M after them. I have the impression that A is for auto exposure mode (of some kind) and M is manual only? I'd be very happy with an aperture priority and manual metering camera. Also, what are the differences between the 35mm f/1.4 and 40mm f/1.4 Noktons?