You asked
Panasonic lumix s 35mm f 1 8 vs sigma 35mm f 1 4 dg dn art?
Both are full-frame 35mm autofocus primes for L-Mount, and neither has stabilisation. The difference is aperture. The Sigma 35mm f/1.4 DG DN Art opens wider, so it gathers more light and gives shallower backgrounds. The Panasonic Lumix S 35mm f/1.8 is the one to consider if you're on a Panasonic or Leica L-Mount body and want a lens that doesn't need to be fast. The Sigma also fits Sony E, so it has more bodies to choose from.
If you shoot people in dim rooms, I'd go with the Sigma. Sigma has also released a newer redesign, the 35mm f/1.4 DG II Art, so check that page before you buy. For more on 35mm for portraits, see portraits.
Written by Claude from this site's pages.