Sigma's ultra-wide Art prime — the world's first AF 20mm f/1.4 with outstanding optics for astrophotography.
The Sigma 20mm f/1.4 DG HSM Art was released in 2015 as an ultra-wide full-frame prime at f/1.4 — providing the widest available maximum aperture at 20mm for any Art-series lens. The bulbous front element prevents conventional filter use. At 950g it is a substantial prime designed for astrophotography and ultra-wide available-light work. HSM provides fast, quiet AF. DG confirms full-frame coverage. Available in Canon EF, Nikon F, and other mounts.
The optical design uses 15 elements in 11 groups. Nine aperture blades. No front filter thread — the bulbous front element prevents standard filter use. At 950g the lens is substantial. Minimum focus distance of approximately 0.276m. HSM motor provides fast, quiet AF with full-time manual override. f/1.4 maximum aperture. DG confirms full-frame coverage.
The f/1.4 at 20mm enables astrophotography exposures of approximately 7-8 seconds (NPF rule) before star trailing on full-frame, capturing an extreme wide-angle star field with more light than the f/2.0 or f/2.8 alternatives at this focal length. For very low ambient light indoor shooting, f/1.4 at 20mm provides the fastest wide-aperture exposure available at this perspective — one full stop faster than f/2.0 alternatives.
On the used market the Sigma 20mm f/1.4 DG HSM Art is available at premium Art-series ultra-wide prime pricing. Condition checks: front element for marks — bulbous with no filter protection — HSM AF response, and barrel condition given the 950g weight. Confirm the mount version — available in Canon EF, Nikon F, and other mounts. Compatible with full-frame and APS-C bodies in the specified mount.