You asked
Is the sigma 85mm f 1 2 dg art sharp wide open?
I don't have sharpness test results for the Sigma 85mm f/1.2 DG Art, so I can't tell you how it performs wide open. The page covers the basics: f/1.2, full frame, Sony E and L-Mount, autofocus, and no stabilisation. It also lists which cameras it fits.
What I can say is that at f/1.2 the depth of field is very thin, thinner than a face in many portraits. Eyes can be sharp while the nose or ears are soft. If you're shooting two people at different distances, stop down to around f/2.8. The Portraits guide explains this in more detail. For how f-numbers affect light and blur in general, see the Lenses guide.
Written by Claude from this site's pages.