You asked
Zeiss loxia 50mm f 2 vs voigtl nder apo lanthar 50mm f 2 aspherical?
Both are 50mm f/2 manual-focus primes for full frame, so the choice mostly comes down to your camera system.
If you shoot Sony E, the Zeiss Loxia 50mm f/2 is a straightforward option. It only mounts on Sony E.
The Voigtländer APO-Lanthar 50mm f/2 Aspherical is the one I'd lean towards. It fits Sony E, Nikon Z and Leica M, so it still works if you change systems later. It's also an apochromatic design, known for very high sharpness and no colour fringing.
On a Sony APS-C body, both behave like a 75mm lens on full frame. If you want a lens for people, this focal length suits portraits well, as the portraits guide explains.
Written by Claude from this site's pages.