Sigma 10-20mm f/3.5 EX DC HSM - £500
The newest version of Sigma's 10-20mm lens boasts a constant aperture, so a relatively fast f/3.5 is available throughout the zoom range. Other headline features include ring-type HSM autofocus with fast, near-silent performance and full-time manual focus override. Build quality feels rugged, and the lens is available in a wide variety of mount options.
Indeed, in our last group test of wide-angle lenses we picked this lens as the top choice for Pentax users, especially as the Pentax 12-24mm lens (not featured this time around) costs nearly double. The Sigma lens is stylishly finished and comes complete with a hood and soft pouch.
Lab results weren't fabulous for the Sigma, but coupled with a Canon EOS 550D in real-world shooting tests, it was sharp even shooting at the widest aperture. Only at the 20mm end of the zoom range did we have to reduce the aperture to f/8 to get sharp images, but the quality drops again at f/16. Sigma's Super Multi-Layer Coatings do a good job of combating ghosting and flare, while maintaining image contrast.
The Sigma 10-20mm optic also resisted vignetting throughout the zoom range, making its large, constant f/3.5 maximum aperture all the more useful. Colour fringing at the 10mm end of the zoom range was also impressively low. Overall, this Sigma lens is an attractive option, especially as it's about £160 cheaper than equivalent Canon and Nikon lenses.
Resolution sharpness test
Centre sharpness is good at 10mm and 20mm, but drops towards the edges. At 16mm sharpness is lower than all the other lenses on test.
Fringing at all focal lengths is minimal at the centre, but towards the edges there are signs of mild blue fringing.
Distortion, while visible at 10mm, is acceptable and can be easily corrected. At 16mm and 20mm distortion is minimal
Image test verdict
Centre sharpness at 10mm and 20mm is good, and fringing and distortion levels are average compared with other lenses on test.