Sigma has a superb selection of wide-angle primes. Michael Topham reviews the latest addition
Sigma 28mm F1.4 DG HSM Art review: Image Quality
Like all of Sigma’s Art-series f/1.4 prime lenses, the 28mm F1.4 DG HSM Art has been optimised for use with today’s high-resolution DSLR and mirrorless cameras. I had originally hoped that I might be able to test an L-mount version of the lens on the Panasonic Lumix S1R, however this isn’t due to arrive until later in the year, possibly December. Instead I opted to test a Canon-fit sample with the 50-million-pixel Canon EOS 5DS R and 22.3-million-pixel Canon EOS 5D Mark III.
A wide-angle lens might not be the first on your radar for shallow-depth-of-field work, but shoot close to subjects wide open at f/1.4 and the lens is capable of creating a pleasing separation with lovely blurred backgrounds. You don’t need to shoot quite as close as you do with a 24mm f/1.4 prime for background blur to be obvious, but you do need to be watchful of your focusing technique when shooting wide open. It’s no bad thing to fire off a few frames of the same scene to ensure you bag one that’s pin-sharp as any small shift in movement is enough to throw the focus slightly off.
Nail the focus wide-open at f/1.4 and you’ll get some very satisfying images that stand apart from wide-angle shots taken at the same focal length on a standard f/4 zoom lens. I wouldn’t go as far as saying that it’s outstandingly sharp in the centre at f/1.4, and it is perceptibly softer in the corners than the centre, but stop down and you do start to notice how it sharpens up across the frame. While the centre of the frame is sharpest at f/4, users will want to dial in an aperture of f/5.6 to locate the sweet spot from edge to edge. Stop down to f/11 and f/16 and the image slightly, but visibly, softens due to diffraction. It makes sense that f/16 is limited as the minimum aperture.
Great strengths of this lens are the way it controls chromatic aberration and distortion. I noticed a hint of green and purple fringing along high contrast edges at wide apertures when inspecting images at close magnification, however this was quickly resolved by increasing the purple and green amount Defringe sliders to a value of 5 in Adobe Camera Raw.
Barrel distortion is low with a slight bend of straight lines towards the edges of the frame, but again it’s not immediately obvious in real-world images. As for vignetting, there’s an obvious fall off in brightness towards the edge at f/1.4, which is clearly illustrated in the sample image above. Stopping down to f/2 sees a big improvement and by f/2.8 corner shading is virtually eliminated.