You asked
Is the sigma 28 45mm f 1 8 dg dn art worth buying used?
Yes, I'd buy this one used. The buying used page makes the case that the used market is one of the best ways to afford good gear, and this lens is a strong reason to go that route. A short zoom that stays at f/1.8 across its whole range is the reason to buy it.
It's a full frame lens for Sony E and L-Mount, and it fits a long list of bodies, from the Sony a7 family to the Leica SL and Panasonic S series. It isn't stabilised, so it leans on good light or a steady hand. When you look at a used copy, check the condition and make sure the autofocus works properly.
Written by Claude from this site's pages.