Sigma 30mm f/1.4 EX DC HSM - £380/$490
With an effective focal length of 45mm on APS-C bodies ranging from the D3100 to the D7000 and D300s, this is potentially an ideal 'standard' prime lens rather than a portrait model. It combines a fast f/1.4 maximum aperture with quick and near-silent HSM (Hyper-Sonic Motor) autofocus that has full-time manual focus override.
Designed for APS-C format bodies, it's large for a 30mm lens, and is bigger and heavier than Nikon's full-frame 50mm f/1.4G. It also has a larger filter thread of 62mm, compared with the Nikon's 58mm. Build quality is solid, but the closest focus distance of 40cm is disappointing for a 30mm lens, the maximum magnification of 0.1x being the lowest on test.
There's a danger of increased vignetting when using a DX lens on an APS-C body, as the image circle is smaller than that in an FX lens. However, this Sigma acquits itself well even at its largest aperture. Centre sharpness is also good, but drops off somewhat towards image edges, and alarmingly so at the borders. Barrel distortion is also noticeable, with the worst results in the group.
The scores don't tell the full story as this lens lacks sharpness towards the edges and corners of the frame.
Sharpness at f/2.8: 1467
Sharpness at f/8: 1889
Sharpness at f/16: 1763
Colour fringing is only slightly noticeable, and is pretty much on a par with that from the Nikon 50mm f/1.8G.
Fringing at f/2.8: 0.16
Fringing at f/8: 0.38
Fringing at f/16: 0.32
Barrel distortion results are the worst in the test group, and are particularly unimpressive for a fixed focal length lens.
Image test verdict
With noticeable barrel distortion and poor edge/corner sharpness, the Sigma struggles to justify its high asking price.