Sigma 10-20mm f/3.5 EX DC HSM £399, $650
A high-spec, constant-aperture lens that’s dropped in price and improved in quality over the last year
Some four years newer than Sigma’s 10-20mm variable-aperture lens, this one used to be much more costly. In the UK the price has dropped over the last year to the point where there’s not a great difference between the two. They look almost identical, although the f/3.5 lens has an auto/manual focus switch and a larger, 82mm, filter thread. Build quality is essentially the same, as are the speed and accuracy of the ring-type ultrasonic autofocus system.
Sigma claims a rather wider maximum angle of view for this lens, at 110 degrees compared with the 102 degrees of its 10-20mm f/4-5.6 lens. In our tests, however, there was no discernible difference between the two. The constant-aperture design is a bonus, giving slightly more than a full extra f/stop at the long end of the zoom range.
In the past, we weren’t bowled over by the sharpness of this lens: it wasn’t quite as sharp in tests as Sigma’s own f/4-5.6 optic. However, there was a marked improvement in the new review lens we tested this time, which proved not only sharper than the other Sigma, but also outclassed every other lens in the group. Correction of colour fringing is another impressive aspect of its image quality.