You asked
What is the leica super apo summicron sl 21mm f 2 asph good for?
The Leica Super-APO-Summicron-SL 21mm f/2 ASPH is a fast, wide prime for full-frame L-Mount cameras. At 21mm it takes in a lot of scene, so it suits landscapes, interiors and street work where the setting matters. Because it's so wide, keep nearby subjects in mind: they get exaggerated, as the Portraits guide warns.
The f/2 aperture gives useful background blur for a lens this wide. The focal length converter explains how aperture and depth of field change across sensor sizes. On APS-C the lens frames like 32mm, which makes it a standard view there.
Good bodies for it include:
- Leica SL3, full frame, the lens's native format
- Panasonic Lumix S5 II, another full-frame option
- Leica TL2, if you want its 32mm-equivalent view
The lens isn't stabilised, so in dim light you'll want to watch your shutter speed.
Written by Claude from this site's pages.