Looking for a sharp medium portrait lens? Many folks prefer that 85mm view because you can still be close to your subject and get very nice blur in your background if shot between f1.4 to f/4. This focal length is great for medium shots only but if you plan on getting head and shoulders I recommend you look into 135mm to avoid elongated noses. I made tests that compare this vintage lens to a newer Nikon lens and threw in a very nice combo with an Olympus camera.
Top: The Summicron produces low contrast images, just add a bit of contrast and you see that it starts to look better than the Nikon if shot at f/2.8. Also notice that I shot with the M. Zuiko 45mm f1.8 which is an amazing little lens.
Top: Summicron slimmer but a tad bit longer with extended hood. It weights more as well.
Top: If you remove the hood on the Nikkor, you can see is a lot smaller. The Summicron has an integrated hood that in the image shown is collapsed in, even with this mode it is still longer than the Nikkor and heavier. Not something Leica users like, one of the great reasons why invest in Leica gear is because it is compact so this vintage Summicron isn’t very popular.
Top: Summicron 90mm color.