I'm a thinking about getting an 18mm Zeiss lens for the M9, but I had a few questions before I go that route (I really can't justify the coin for the Leica SE!).
I know about the distortion and the red edge issues... but I don't know about the lens mount. Does the mount come correctly machined to allow it to be coded as an 18mm or as the 21mm pre-ASPH? Do I need to be getting a different mount so that the framelines are set to the 'correct' setting? What is the correct setting for the 18mm?
I think that's it. The archives have a lot of GREAT info on this lens vs. the SE, so most other questions have been answered.