Conclusion

As with other Sigma lenses that we've recently reduced, the Sigma 120-300mm F2.8 DG OS HSM S once again offers a unique and importantly high-quality alternative to similar lenses from Canon and Nikon. Neither of those companies have such a fast telephoto zoom in their ranges, or a similar focal range.

Build quality is again excellent, with the brass lens mount and sober all-black design adding to the high-quality feel and the dust/splash-proof construction adding some peace of mind, plus there's a very good lens hood and padded case. It is a heavy lens, though, and therefore best suited to life on a tripod/monopod. Focusing was very quick on the Canon EOS 5D Mark III that we tested the lens with, and manual focus over-ride at any time is a great feature, as is the effective built-in optical image stabilisation system.

The Sigma 120-300mm F2.8 DG OS HSM S is tack-sharp at both the centre and edges of the frame from f/4-8 at all focal lengths, with overall performance best at 120-200mm. Vignetting at wide-open apertures is the only other real optical issue of note, and this can be easily corrected in post-production. If we had one complaint about the Sigma 120-300mm F2.8 DG OS HSM S, it's the fact that it stops at 300mm - we'd add a 1.4x teleconvertor to extend the reach to 420mm at the slight expense of making the maximum aperture a still very fast f/4.

Even the price of the Sigma 120-300mm F2.8 DG OS HSM S is attractive, undercutting the main rival lenses from Canon and Nikon. We can strongly recommend the new Sigma 120-300mm F2.8 DG OS HSM S as a fast telelphoto zoom lens that delivers excellent results on the latest full-frame DSLRs.

Ratings (out of 5)
Design	4.5
Features	4.5
Ease-of-use	4.5
Image quality	4.5
Value for money	4.5