You asked
Is the sigma 105mm f 1 4 dg hsm art good on aps c?
Yes, it works well on APS-C, though it's a big, heavy lens for a small body. Your crop turns it into a tighter telephoto. On Sony E, Nikon F or L-Mount it frames like about 158mm on full frame, with depth of field close to f/2.1. On Canon EF it's about 168mm, at roughly f/2.2. That's a proper headshot lens with lovely background blur.
Good APS-C partners for it include:
The weight is the catch, so balance matters. If you want something lighter for portraits, the portraits guide covers the 85mm and other options.
Written by Claude from this site's pages.