You asked
Panasonic lumix s 18mm f 1 8 vs viltrox af 16mm f 1 8?
Here is what the site says about that.
From Panasonic Lumix S 18mm f/1.8: Panasonic Lumix S 18mm f/1.8: A prime lens by Panasonic for Full frame cameras, 18mm f/1.8. Specs - Maker: Panasonic - Focal length: 18mm (prime) - Maximum aperture: f/1.8 - Made for: Full frame sensors - Mounts: L-Mount - Stabilised: no - Autofocus: yes What it frames like - On full frame (L-Mount): as marked, 18mm. - On APS-C (L-Mount): like 27mm on full frame; f/1.8 gives about the depth of field of f/2.7 there. ...
From Viltrox AF 16mm f/1.8: Viltrox AF 16mm f/1.8: A prime lens by Viltrox for Full frame cameras, 16mm f/1.8. Specs - Maker: Viltrox - Focal length: 16mm (prime) - Maximum aperture: f/1.8 - Made for: Full frame sensors - Mounts: Sony E, Nikon Z, L-Mount - Stabilised: no - Autofocus: yes What it frames like - On full frame (Sony E, Nikon Z, L-Mount): as marked, 16mm. - On APS-C (Sony E, Nikon Z, L-Mount): like 24mm on ...
Quoted from this site's pages.