Rangefinder lenses for Leica M are compact and high performance, but subject to ray angle issues when used on mirrorless cameras. But what about a 50mm rangefinder lens? Isn’t that a long enough focal length? Nope.
Lenses are always covered in their native Guide, accordingly in Guide to Leica I show what the Leica 50/2 APO can do (the best M lens of all), along with the classic optical formula Zeiss ZM 50mm f/2 Planar for comparison:
This general question is well answered here and surely ought to be read by owners of Leica M and Zeiss ZM rangefinder lenses contemplating a mirrorless future, since a 50mm focal length is more “friendly” than shorter focals.