So many good and great 50mm lenses in M mount these days; Leica, Zeiss ZM, Cosina Voigtlander, or get an adapter and use an old Canon, German Zeiss, Nikon, ect. It really depends on your taste. Not really a 50mm guy for rangefinders anymore, and I only own a late dual range Summicron now, but the 4th/5th optical version Summicron are great all rounders. Never had any issues with those lenses; they seem to do everything good. The dual range Summicrons have been hit or miss for me -- two I've used have been very good, one other not so much. I found the 50mm Summilux Asph too big, but great optics. I like the old Sonnars for their character -- the Canon 50mm/1.5 or any old Zeiss 50mm/1.5. They're smaller too, even with adapter. Tom A. use to really sing the praises of the ZM 50mm/1.5 (another Sonnar). The ZM 50/2 Planar is very contrasty. Voitglanger has interesting possibilities, especially if you're interested in super fast lenses. I'm always trying to tell myself how I really need a 50mm Nokton f/1.2. So far, I've been able to resist. And if you want to wait a bit, I have a feeling Voigtlander will come out with a 50mm f/2 ASPH in the next year or so. So many great, affordable options in this focal length. Sort of glad I no longer own an M3, because I would probably have a different 50 for each day of the month. 🙂 Good luck.
