Sigma's early wide-angle zoom for Canon EF — the 17-35mm f/2.8-4 EX HSM.
The Sigma 17-35mm f/2.8-4 EX HSM Aspherical is the Canon EF mount version of Sigma's early wide-angle zoom also described in Nikon F (ID 3581) and Sony A (ID 3780). The variable aperture starts at a useful f/2.8 at 17mm. EX professional build with HSM quiet AF. A budget wide-angle zoom from an earlier generation of Sigma optics.
Optical performance is decent for the era. Centre sharpness is good at wider focal lengths. HSM provides fast, quiet AF on Canon bodies. The aspherical element helps control aberrations. DG coatings reduce sensor reflections. The f/2.8 at 17mm is useful for ultra-wide work. Corners soften at wider apertures.
Canon EF mount. Filter thread is 82mm — large. Weight is approximately 660 grams. Build quality is solid EX professional. No image stabilisation. The 17-35mm range covers useful ultra-wide to moderate wide perspectives on full-frame Canon bodies. Superseded by much better modern alternatives.
Available at very low used prices. Check AF and zoom operation. Thoroughly superseded by modern alternatives. The Canon EF 16-35mm f/4L IS or Sigma 14-24mm f/2.8 Art are dramatically better. Only of interest at very low prices for budget full-frame wide-angle on Canon.