Sigma 18-35mm f/1.8 DC HSM review
Similarly, although technical testing revealed a hint of chromatic aberration at 18mm (and the tiniest residue at 24mm too) there were no signs of colour fringes in any real-world pictures. Distortion was equally well controlled, with just the faintest trace of barrel curvature at 18mm and converting to an equally negligible amount of pincushion distortion at 35mm.
MTF curves for all three focal-lengths sat aboce 0.3 cycles-per-pixel from f/4 to f/11 and only dipped slightly below the important 0.25 cycles per pixel threshold at the widest aperture. Optimum performance is obtained between f/5.6 and f/8, with sharpness improving as the focal-length is increased. Between f/4 and f/11 the zoom's resolution exceeds 0.3 cycles-per-pixel at all focal lengths.
In the field the biggest plus-points were the ability to take pictures in low-light conditions and the eye-catching nature of the close-range pictures that could be created: the most noticeable drawback was the considerable weight of the lens. There were a couple of occasions when focussing didn't turn out to be completely sharp, despite the in-focus indicator having been lit, but it is impossible to say whether that was caused by the lens itself or the host camera body used for this test (Canon EOS 50D). Nevertheless, we are only talking here about a slight loss of "bite": at no stage were any pictures taken that could be described as being specifically unsharp.
Perhaps the best news of all about this lens is its price. It would be easy to assume that a lens as revolutionary and quality-rich as this would easily tip £1000 but in fact Sigma has positioned it comfortably below this and street prices can be found for a little as £649.
Unless something truly incredible is waiting around the corner, Sigma's 18-35mm f/1.8 A-series lens will surely be the wide-angle zoom of the year for 2013.