Jonathan_100
Jonathan
I'd go with the Nokton 50. I have one and love it--great shooter in low light. I can't speak to the 40 directly. Some don't like the bokeh, and , but I've seen a lot on the used market which tells me that it might not be as successful shooter as the 35 or 50.
Jonathan
Jonathan
ClaremontPhoto
Jon Claremont
I use 40mm's as standard. Much better than either 35mm or 50mm for my use. YMMV.
mc_vancouver
Established
I'm still debating a trade of my 50 for your 40, but I don't know if I like the tabs for focus and aperture rings on the 40. There's more space for the fingers on the 50, more of a classic styled lens. That said, the 40 would be ideal for my R3M. There's another thing to think about: in digital realm, assuming one has or gets either the Rd1 or the M8, the 40 becomes a fifty or sixty, the fifty gets up to near 70mm equivalent, approximately.