This professional standard lens impressed our tester. Find out why by reading the Sigma 10-20mm f/3.5 EX DC HSM lens review.
Sigma 10-20mm f/3.5 EX DC HSM Review
The design is compact but very usable. The rearward zoom ring is a shade on the narrow side but has just the right feel, whereas the similarly-narrow forward focusing ring is a bit on the stiff side. Sacrificing the intervening focused-distance window would allow the zoom ring to be made a little wider, but I’m not sure that all professionals are ready to buy lenses with no visible focusing information.
The manual focusing ring does not rotate in AF mode, which improves handling by removing restrictions on where the user’s fingers can grip the lens. Equally importantly, manual focusing adjustments can be applied without having to switch to MF mode. AF operation is quick and genuinely quiet thanks to a Hyper-Sonic Motor (HSM).
Given the extreme angles of view offered by this lens it would be understandable for there to be visible distortion, but in fact what little exists is hardly worth mentioning. Not only can this lens be used to capture sweeping vistas but also it can be used in cramped interiors without fear of bending the walls (provided that great care is taken to align the camera vertically and horizontally). The f/3.5 aperture gives good viewfinder brightness, and the f/22 minimum setting resists the temptation to stray into seriously diffraction-limited territory.
About a year ago, when Sigma’s variable-aperture (f/4-5.6) 10-20mm zoom was tested, a doubt was expressed about whether the then-forthcoming f/3.5 lens would really be much better optically. The answer, as demonstrated by the accompanying MTF graph, is a definite yes: the latest version has stunning resolution and performs brilliantly in real-world use.
The lens records 0.3 cycles-per-pixel or better from wide-open right through to f/11 and is still above the critical 0.25 cycles-per-pixel level at f/16. It is true that the resolution is much lower at f/22, but there is little reason to set so small an aperture on a lens such as this.