You asked
Is the voigtl nder apo lanthar 50mm f 2 aspherical good on aps c?
Yes, with a caveat. This is a full-frame lens, but it mounts on APS-C Sony E and Nikon Z bodies. There it frames like a 75mm lens, and f/2 gives about the depth of field of f/3. That makes it a strong portrait lens, since the Portraits guide already treats a 50mm on APS-C as a classic 75-80mm portrait focal length. It's known for very high sharpness and no colour fringing, so the image quality holds up. The main trade-offs are that it's manual focus only and not stabilised.
Good APS-C bodies to pair it with include the Sony a6400, the Sony a6700 and the Nikon Z50 II. If you're still choosing a first lens, the Lenses page covers the basics.
Written by Claude from this site's pages.