Sigma 8-16mm f/4.5-f/5.6 Review
The new Sigma 8-16mm f/4.5-f/5.6 is a promising new ultra wide angle lens for APS-C and smaller formats. On Pentax it offers an incredibly wide 120° diagonal field of view (112° horizontal by 89° vertical), all with no fisheye distortion. The question is, does it perform well given its extreme specifications?
The lens is a joy to use. The fit and finish is typical of Sigma EX lenses (even though this isn’t officially an “EX” lens). The zoom ring is smooth, but a tad narrow. The focus ring is nicely weighted for an AF lens; providing a reduction system where turning the focus ring 30° would equate to roughly 15° change on the distance scale. The lens has an AF/MF switch that can be used for focus trap, and manual focus override (equivalent to Pentax’s quick shift focus) that is smooth and easy to use.
The lens cap is a metal ring with a 72mm traditional center pinch lens cap attached. Although you can use 72mm filters with this ring, they will vignette at all focal lengths including 16mm. Focus with the HSM is fast in silent in phase detect mode (traditional), but extremely slow in contrast detect mode (live view). Focus is typical of Pentax SDM lenses, where it isn’t necessarily faster than traditional screw-drive, but offers smooth and quiet operation.
The size of the lens is also nice. It is significantly longer than the Sigma 10-20mm f/4-f/5.6, but also significantly narrower (72 instead of 77mm cap), making it more slender and easier to put in a camera bag. It is almost exactly the size of a 14.5 oz can of Hunt’s Tomato sauce I have in my cupboard (not counting the mount).
There are a couple of usability issues with the lens. The first is that the Pentax camera doesn’t register the focal length in the EXIF for focal lengths less than 10mm. It will show as — and this poses a problem for Adobe Lightroom 3’s lens correction, that needs to know the focal length to apply the proper corrections. The second is that it is painfully slow to auto focus in live view on the camera. Much slower than other lenses I have used, taking maybe 5 seconds to achieve focus in good light (My DA 16-45mm is maybe 3 seconds). Both these would likely be fixable by firmware updates of the camera or lens.
The lens feels great mechanically and wouldn’t feel out of place alongside pro level glass, but the question remains, how is the lens optically? It is a 2x zoom with an extreme field of view, being significantly wider than any other APS-C lens.