You asked
Nikon af s 85mm f 1 4g vs sigma 85mm f 1 4 dg hsm art?
They frame and perform much the same on a Nikon body. Both are 85mm f/1.4 autofocus primes for full frame, neither is stabilised, and on APS-C both give the same 128mm-equivalent view with depth of field like f/2.1.
The difference is mounts. The Nikon AF-S 85mm f/1.4G is Nikon F only. The Sigma 85mm f/1.4 DG HSM Art also comes in Canon EF, Sony E and L-Mount. If you shoot Nikon and don't plan to switch, I'd pick the Nikon, since it's the classic portrait lens for that system. If you might change brands later, the Sigma keeps its value. For the bigger picture on focal lengths, see portraits.
Written by Claude from this site's pages.