You asked
What is the sigma 24 70mm f 2 8 dg dn art good for?
The Sigma 24-70mm f/2.8 DG DN Art is a full frame standard zoom, and it suits most everyday shooting. On Sony E and L-Mount full frame bodies it covers 24-70mm, and its constant f/2.8 aperture keeps exposure steady as you zoom. That helps with people, food, and low light, where the wide aperture gives faster shutter speeds and more background blur.
It's also a flexible choice for travel and landscapes, since 24-70mm covers most scenes. On APS-C it frames like 36-105mm, which works well for portraits.
This is the first version, and the II has since replaced it, so check the Sigma 24-70mm f/2.8 DG DN II Art page too. For more on why f/2.8 matters, see Lenses.
Written by Claude from this site's pages.