Sigma's early full-frame ultra-wide zoom — 15-30mm at f/3.5-4.5 before modern alternatives.
The Sigma 15-30mm f/3.5-4.5 EX DG is an early full-frame ultra-wide zoom predating the numerous modern alternatives. It provided 15-30mm coverage — wider at 15mm than most competitors of the era — on full-frame DSLRs.
Optically acceptable — sharp in the centre with the 15mm providing dramatic ultra-wide coverage. EX professional build quality. Variable f/3.5-4.5 aperture. No stabilisation. Aspherical elements help control distortion.
Available for Canon EF, Nikon F, and other mounts. Bulbous front element — no standard filter thread. Approximately 740g. No weather sealing. Full-frame coverage. EX designation — quality construction.
Available used very cheaply. The Tamron 15-30mm f/2.8 VC is dramatically better with VC and constant f/2.8. Modern alternatives are vastly superior. Only worth considering at bargain prices. The 15mm was impressively wide for its era.