I recently bought a Sony A7 II moving away from Nikon DSLRs (I owned a D800E) and I am using (with adapters) all my other lenses like the M42s, the Nikons of course and the Leica M-mount lenses I have, made by Voigtlander.
One lens that I simply love is the Voigtlander Color Skopar 21/4. It’s just a marvellous, amazing lens. Sharp (maybe even sharper than the Leica equivalents), great colour rendition, amazing black and white. I have been using it on my Bessa R3A for years now.
I thought I’d share my experience of using this lens on a digital mirrorless camera. In my case, Sony A7 II. Here it is mounted on the camera, via a Commlite close-focus Leica M adapter.