Sigma's earlier 24-70mm f/2.8 for DSLRs — pre-Art line with HSM motor and EX professional build.
The Sigma 24-70mm f/2.8 EX DG HSM launched in 2008 as Sigma's professional constant-aperture standard zoom for full-frame DSLRs. Predating the Art lineup, it offered a budget alternative to the Nikon 24-70mm f/2.8G and Canon 24-70mm f/2.8L with EX-series build quality.
Optically decent — sharp in the centre but noticeably softer than the first-party alternatives, particularly in the corners. The constant f/2.8 aperture is useful for events and low light. HSM motor provides fast, quiet AF with full-time manual override.
Available in Nikon F mount and others. 82mm filter thread. Approximately 790g. No weather sealing. Full-frame coverage. EX designation — quality metal barrel construction. Minimum focus distance 38cm. No stabilisation.
Available used very cheaply. The Art-line 24-70mm f/2.8 DG OS HSM (2017) is dramatically better. The first-party Canon and Nikon 24-70mm f/2.8 lenses also outperform it. Only worth considering at bargain prices where the constant f/2.8 is needed on a tight budget.