The Summicron-M 50mm f/2 is an impressive lens. It shows very good resolution across the frame wide open, and excellent sharpness when stopped down to f/4 or f/5.6. Distortion is no issue at all.

Vignetting is fairly pronounced wide open. When 6-bit coded, the camera reduces vignetting considerably, however one should be aware of the drawbacks of this approach regarding noise. CAs are well under control, as is bokeh fringing.

Bokeh is a bit nervous wide open, but improves by stopping down slightly. For smoothest image bur, one shout set the lens to f/2.8 or f/4 (if the subject allows). Unfortunately, background highlights already form polygons at this aperture setting.

The build quality of the lens is truly excellent, as you'd expect from a Leica lens. It's a joy to use.

The only real drawback of the lens is its rather hefty price (for a normal prime). Apart from that: highly recommended!