You asked

What is the panasonic lumix s 100mm f 2 8 macro good for?

Here is what the site says about that.

From Panasonic Lumix S 100mm f/2.8 Macro: Panasonic Lumix S 100mm f/2.8 Macro: A macro lens by Panasonic for Full frame cameras, 100mm f/2.8. Specs - Maker: Panasonic - Focal length: 100mm (macro) - Maximum aperture: f/2.8 - Made for: Full frame sensors - Mounts: L-Mount - Stabilised: no - Autofocus: yes What it frames like - On full frame (L-Mount): as marked, 100mm. - On APS-C (L-Mount): like 150mm on full frame; f/2.8 gives about the depth of field of f/4.2 there. ...

From Portraits: The lenses: - 50mm f/1.8. The cheapest great lens in photography, made for almost every mount. On full frame it's a natural, slightly tight view; on APS-C it behaves like a classic 75-80mm portrait lens. If you buy one lens for people, buy this. - 85mm f/1.8. The classic full-frame portrait lens: flattering perspective, soft backgrounds, comfortable working distance. On APS-C, a 56mm f/1.2 to f/1.4 plays the same role. - 35mm ...

Quoted from this site's pages.

From these pages