Sigma's budget ultra-wide zoom for APS-C DSLRs, available across all major mounts.
The Sigma 10-20mm f/4-5.6 EX DC HSM is a budget ultra-wide zoom designed for APS-C DSLRs, launched around 2005. Covering a dramatic 15-30mm equivalent range, it brought ultra-wide photography to budget-conscious shooters across Canon, Nikon, Sony, Pentax, and Sigma mount systems.
Optical quality is reasonable for the price with decent centre sharpness but soft corners, particularly wide open at 10mm. Distortion is well-controlled for an ultra-wide. The HSM motor provides autofocus though it is an older design. Build is solid plastic. There is no image stabilisation.
Available in Canon EF-S, Nikon F, Sony A, Pentax K, and Sigma SA mounts. Filter thread is 77mm. A later f/3.5 version offers a faster constant aperture with improved optics. The Sigma 10-20mm f/3.5 EX DC HSM is the recommended version if choosing between the two.
Very cheap used in all mounts. Check HSM motor operation and front element for damage which is common on ultra-wide lenses. The f/3.5 version is worth the modest premium for its wider constant aperture. An affordable entry into ultra-wide photography.