I can't say anything about the R3A because I use my Nokton on another make of camera. But thats not important.
What is important is that the 40mm Nokton is a fine lens. Mine is the MC version and it renders in a very similar way to the Canada made 35mm Summilux, it even looks similar at a glance. So wide open it renders a pleasant 'glow' to the image, and it sharpens up and calms down as you stop down. It is also very small for an f/1.4 lens, but it is easy to handle at the same time.