You asked
What is the pentax smc da 35mm f 2 4 al good for?
The Pentax smc DA 35mm f/2.4 AL is a small prime for APS-C Pentax K bodies. On an APS-C camera it frames roughly like a 52mm lens on full frame, and f/2.4 gives about the depth of field of f/3.6. It's autofocus but not stabilised, so keep the shutter speed up in dim light.
I'd use it for environmental portraits that show where someone is, and for small groups. It's a good everyday walk-around lens for people, street and general daily shooting. f/2.4 isn't especially fast, though, so if low light is your main worry, the portraits guide points to the faster 35mm f/1.4 to f/1.8 options for APS-C. For the broader picture of building a kit, see your first lenses.
Written by Claude from this site's pages.