Well, shot on the 4:5 APS-C sensor of the more recent Leica CL. When I read the thread title, I thought briefly it may have been the older Leica CL (which I have) that utilizes film cartridges and such. Images on 4x5 film can sometimes be really, really impressive. Nice that some folks find the summicron 50mm on digital APS-C to be similar. And so much easier in terms of processing, etc. I find this mildly distressing as I continue to string along my film addiction with MF and LF endeavors...
Indeed, Leica lenses are darn nice. Sure, there's some other lenses are also darn nice (e.g., Zeiss). But whew! I do notice the quality of images from the summicron...
My favorite 50mm summicron is the v4. Mine orginally had a "tiger claw" focus tab. Nothing wrong with that, but when I had DAG overhaul the lens, I asked for a "half moon" focus tab replacement. Been darn happy ever since. The v4 lenses and v5 lenses are supposed to be the same except for the built-in hood on v5 lenses. Good....now I won't worry about needing the v5. The APO is something else entirely, and I'm letting that one sit out. I only have so much $$$ to apply to my hobby and it don't make sense to send it all (and then some to come!) just to one 50mm lens.
Long live the v1 through v5 summicrons (50mm). Such amazing lenses, eh?