Sigma's hugely popular APS-C constant f/2.8 standard zoom — sharp, stabilised, and excellent value.
The Sigma 17-50mm f/2.8 EX DC OS HSM launched in 2011 as a constant f/2.8 standard zoom for APS-C DSLRs. Covering 25.5-75mm equivalent on Canon, it became one of the most popular third-party lenses ever made — offering professional-grade f/2.8 speed at a fraction of first-party prices.
Optically very good — sharp across the frame at most focal lengths with impressive centre performance. The constant f/2.8 aperture is a genuine advantage for events and low light. OS stabilisation provides approximately 4 stops of correction. HSM motor is fast and quiet.
Available in Canon EF-S mount and others. 77mm filter thread. Weighs approximately 565g. No weather sealing. DC designation means APS-C coverage only. Minimum focus distance 28cm. EX build quality with quality materials.
Extremely common used and outstanding value — one of the best lens bargains in photography. Check AF calibration — use a USB dock if available. The Tamron 17-50mm f/2.8 VC is the main alternative. An essential recommendation for APS-C DSLR shooters wanting f/2.8 on a budget.