For what it's worth. Here's a comparison of three 35mm lenses. Both Leica lenses have been thru a complete overhaul at Kanto camera. The Zeiss lens is brand new.
I decided to take a test shot since I had all three lenses with me. I don't see much difference between the Leica lenses. Zeiss seems to have the best color, contrast and sharpness.
The light outside was flat
1. shot at f/8, I can't remember the shutter speed but I kept it fixed. (around 1/125th)
2. No filter on any of the lenses
3. All focused to infinity
4. Provia 100f (developed at Fujifilm in Japan)
35mm Summicron v1 (8-element) screw mount with Leitz adapter (1959)
35mm Summicron v2 (6-element) m-mount (1970)
35mm Zeiss Biogon ZM f2.8

I decided to take a test shot since I had all three lenses with me. I don't see much difference between the Leica lenses. Zeiss seems to have the best color, contrast and sharpness.
The light outside was flat
1. shot at f/8, I can't remember the shutter speed but I kept it fixed. (around 1/125th)
2. No filter on any of the lenses
3. All focused to infinity
4. Provia 100f (developed at Fujifilm in Japan)
35mm Summicron v1 (8-element) screw mount with Leitz adapter (1959)

35mm Summicron v2 (6-element) m-mount (1970)

35mm Zeiss Biogon ZM f2.8
