You asked
What is the sony fe 20 70mm f 4 g good for?
The Sony FE 20-70mm f/4 G is a full frame standard zoom. Its wide end at 20mm suits landscapes and architecture, and the 70mm end covers everyday scenes, so it works as a general-purpose kit lens. On APS-C Sony E bodies it frames like 30-105mm on full frame, which is a handy standard range there too.
It's a good match for landscapes. f/4 is plenty when you'll mostly shoot between f/8 and f/11, and it's lighter and cheaper than the f/2.8 zooms. Its f/4 maximum is less useful in dim light or for a blurry background, so it's not the lens for that. It also isn't stabilised, so keep your shutter speed up when you're handheld.
It fits a long list of Sony E bodies, from the a7 to the a7R VI, plus several APS-C models. See the lens page for the full list, landscape for how I'd use it outdoors, and your first lenses if you're building a kit.
Written by Claude from this site's pages.