Sigma's extreme APS-C ultra-wide zoom — 12-24mm equiv at variable aperture with rectilinear correction.
The Sigma 8-16mm f/4.5-5.6 DC HSM was released in 2010 as an ultra-wide zoom for APS-C crop-sensor bodies, covering 12-24mm full-frame equivalent. Fifteen elements in 11 groups. Seven aperture blades. No filter thread — the bulging front element prevents standard filter attachment. At 555g. 0.24m MFD. HSM autofocus.
Fifteen elements in 11 groups. Seven aperture blades. No filter thread (bulging front element; rear gel filters only). At 555g the lens is moderate. Minimum focus distance of 0.24m. HSM motor for fast, quiet AF. Variable aperture from f/4.5 at 8mm to f/5.6 at 16mm. DC (APS-C) image circle — APS-C / DX only, not full-frame compatible.
The 8-16mm range covers 12-24mm equivalent on APS-C — from near-fisheye ultra-wide to moderate wide. The 8mm end at 12mm equivalent provides an extreme wide perspective. The absence of a filter thread is the primary operational limitation for photographers using ND or polarising filters; only rear gel filters can be accommodated. Available in Canon EF, Nikon F, Pentax K, Sony A, and Sigma SA mount variants.
On the used market the Sigma 8-16mm f/4.5-5.6 DC HSM is affordable as an APS-C ultra-wide zoom. Condition checks: HSM AF response, front element for marks (inspect carefully given the exposed bulging design), zoom ring smoothness. No filter thread. APS-C only. Confirm mount variant matches your body before purchase.