Careful, heading out and buying a 35 Cron ASPH for using only on the RD-1!
I do not know, if this is limited to my RD-1 and 35 Cron ASPH, but I can think of no logical reason, it should not be a systematic incompatibility with the two items.
My 35 Cron ASPH shows on the RD-1 very strong Aspherical aberration and is extremely (I mean really extremely) flare prone wide open.
This is unlikely an issue, stopping the lens down during daylight. It is so strong though, that night shots with any bright light source within the frame (street lantern, car headlights, etc) are unusable.
Try the lens before buying!
Oh and for the people with doubt - on film, my 35 Cron ASPH is fine (by far not a 50 Lux ASPH, regarding flare, but fine).
On the M8.2, it totally transferred into a very strong performer, it's flare being reduced strongly and with NO perceivable aspherical aberration at all in the images, wide open.
Something with the RD-1 is just not compatible with the 35 Cron (I suppose micro lenses on the Leica sensor and the optimization of DNG data in camera, based on the 6bit code information of the lens are to be accounted).