The Sigma 28-45mm f/1.8 DG DN Art is a narrow-range zoom with an unusually wide maximum aperture for its category. f/1.8 across a zoom range is a specification that did not exist at a practical price and size before the large-diameter mirrorless mounts made the optical corrections feasible. The result is a zoom that behaves like a fast prime — subject separation, low-light capability, and rendering quality at maximum aperture — with the flexibility to shift perspective without changing lenses.