Sigma's first-generation ultra-wide zoom for APS-C DSLRs, covering a dramatic 15-30mm equivalent range.
The Sigma 10-20mm f/4-5.6 EX DC (2004) was Sigma's first ultra-wide zoom designed specifically for APS-C DSLRs, delivering an effective 15-30mm equivalent field of view. The EX designation placed it in Sigma's above-standard optical quality tier; the DC designation confirms the APS-C-only image circle. Released during the early DSLR era when ultra-wide options for APS-C cameras were limited, it became a popular choice for landscape, interior, and architectural photographers using Nikon DX, Canon EF-S, Pentax APS-C, and Sony A-mount systems.
10-20mm focal length, f/4-5.6 variable aperture. EX class optical quality. DC = APS-C image circle only (will vignette heavily on full-frame). 82mm filter thread. At approximately 500-520g. Minimum focus distance approximately 0.24m. Available in Canon EF, Nikon F, Pentax K, Sigma SA, and Sony A mounts. Conventional DC motor AF on most versions — audible and adequate for stills; the later HSM variant (id=4913) uses Hyper Sonic Motor for quieter AF. No weather sealing. Variable aperture from f/4 at 10mm to f/5.6 at 20mm.
The 10-20mm range provides an extreme wide-angle rectilinear perspective for interiors, architecture, landscape, and environmental portraiture. On APS-C the 10mm end delivers a strongly wide view; barrel distortion at the extreme wide end is correctable in post-processing on most raw processors. Using this lens on a full-frame body produces heavy vignetting and is not recommended. EX optical quality delivers good centre sharpness stopped down to f/8; wide-open corner performance is softer, typical for ultra-wide zoom designs of this era.
On the used market the Sigma 10-20mm f/4-5.6 EX DC is a capable and affordable APS-C ultra-wide. Confirm whether the copy has the conventional DC motor or the less common HSM motor before purchase — the HSM is quieter for video use. Inspect the 82mm front element for coating marks or fungus given its large exposed surface. Test AF response at both 10mm and 20mm ends. The Sigma 10-20mm f/3.5 EX DC HSM (2008) provides a faster constant aperture and universal HSM motor at a modest premium. Compatible with APS-C bodies only; use on full-frame produces heavy vignetting.