You asked
Voigtl nder color skopar 35mm f 3 5 aspherical vs zeiss c biogon t 35mm f 2 8 zm?
Both of these are 35mm manual-focus primes for full-frame Leica M bodies, and neither has stabilisation. They fit the same list of M cameras, from the M9 through the M11, so the choice comes down to aperture.
I'd pick the Zeiss C Biogon T\* 35mm f/2.8 ZM if you shoot indoors, at dusk, or want a little more background separation. Its f/2.8 opens about a third of a stop wider than the alternative.
The Voigtländer Color-Skopar 35mm f/3.5 Aspherical is the slower of the two. If most of your shooting is in good daylight, such as street, travel, or landscapes, f/3.5 will do the job, and you won't miss the extra stop much.
For how aperture changes depth of field on different sensors, see the focal length converter.
Written by Claude from this site's pages.