Sigma 8-16mm f/4.5-5.6 DC HSM - £550
The newest lens tested, Sigma's 8-16mm lens is the widest zoom lens on the market for APS-C cameras. The zoom range is equivalent to 12-24mm in Nikon, Pentax and Sony fit, and 13-26mm in Canon fit.
Like Sigma's 4.5mm circular fisheye lens (also for APS-C cameras), the new 8-16mm has a slip-over tube onto which the lens cap fits, or on which you can attach filters with a 72mm thread. The tube causes extreme vignetting at anything other than the longest 16mm zoom setting, so it needs to be removed in nearly all shooting scenarios. A petal-shaped hood is built into the lens, which helps to protect the front element from knocks and scrapes.
A trade-off of the extremely wide angle of view is that the lens isn't the sharpest tool in the box. However, sharpness is respectable right into the edges and corners of the frame, and this is retained very well even when shooting at the largest available apertures. The HSM (HyperSonic Motor) autofocus is quick, quiet and accurate, and comes with full-time manual override, though the focus ring is a little stiff.
Vignetting is noticeable when combining the shortest focal length of 8mm with the widest aperture of f/4.5, but drops considerably at f/5.6 and isn't an issue at f/8 or narrower. Again, considering its extreme wide-angle potential, distortion and colour fringing were moderate, and the Sigma performed well in our field tests.
Resolution sharpness test
Sharpness at all focal lengths is average compared with the other Canon fit lenses. Best performance is gained at the 12mm centre point.
At 8mm and 12mm mild green fringing occurs at the mid frames, and blue at the edge. Centre fringing is minimal at all focal lengths.
Pronounced barrel distortion reflects the 8mm focal length, yet it is still less than on the Nikon. Pinch distortion is just visible at 16mm.
Image test verdict
As expected from the 8mm focal length barrel distortion is heavy, but sharpness and fringing is comparable to other Canon fit lenses.