Sigma's extreme 10x zoom — 50-500mm full-frame with OS stabilisation, nicknamed 'Bigma' for its size.
The Sigma 50-500mm f/4.5-6.3 APO DG OS HSM is a superzoom telephoto for full-frame Canon EF and Nikon F bodies, covering 50-500mm in a single zoom. APO (apochromatic) correction via 4 SLD glass elements. OS optical stabilisation. HSM autofocus. At 1,970g and 95mm filter thread it is very heavy. Nine rounded aperture blades. 0.50m MFD at 50mm, 1.80m at 500mm.
The optical design uses 22 elements in 16 groups including 4 SLD (special low dispersion) elements. Nine rounded aperture blades. The 95mm filter thread. At 1,970g the lens is very substantial. Minimum focus distance of 0.50m at 50mm (1.80m at 500mm). OS provides optical stabilisation. HSM provides fast, quiet AF. Variable aperture from f/4.5 (50mm) to f/6.3 (500mm).
The 10x zoom range from 50mm to 500mm provides the widest continuous superzoom range in a single full-frame telephoto lens. At f/6.3 at 500mm, adequate exposure requires outdoor daylight or significant ISO. The APO SLD glass designation targets the chromatic aberration that becomes pronounced at telephoto focal lengths in variable-aperture super-telephoto designs.
On the used market the Sigma 50-500mm f/4.5-6.3 APO DG OS HSM is affordable for a 500mm full-frame superzoom. Condition checks: OS engagement, HSM AF response, 95mm front element for marks, zoom ring smoothness across 10x range. The 1,970g weight requires tripod or monopod support at 500mm. Compatible with Canon EF or Nikon F bodies depending on version.