Sigma's fast DSLR telephoto zoom with OS stabilisation, competing with first-party 70-200mm f/2.8s.
The Sigma 70-200mm f/2.8 EX DG OS HSM launched around 2010 as Sigma's first stabilised fast telephoto zoom. Competing with Canon and Nikon's professional 70-200mm f/2.8 lenses at a lower price, it brought constant f/2.8 telephoto capability to budget-conscious professionals.
Optical quality is good with respectable sharpness across the range. OS provides approximately 4 stops of stabilisation. HSM autofocus is fast and quiet. Build is solid but not weather sealed. At 1430g it is similar weight to first-party alternatives.
Available in Canon EF, Nikon F, Sony A, and Sigma SA mounts. Filter thread is 77mm. The Sigma 70-200mm f/2.8 DG DN OS Sports is the modern mirrorless successor with dramatically improved optics. The EX version is the DSLR-era offering.
Good value used in all mounts. Check OS operation, HSM motor, and AF consistency. The lens offers professional f/2.8 capability at a discount versus first-party. Some copies benefit from Sigma USB Dock calibration.