Sigma combines super-wide, super-fast and superfeatured to offer night-sky enthusiasts lower ISO settings and plenty of control, says Damien Demolder
If you want a 14mm lens for your full-frame mirrorless camera, with autofocus and a maximum aperture of f/1.4, the Sigma 14mm F1.4 DG DN Art is the only game in town.No one else makes anything quite like it, with the closest alternative being the Sony FE 14mm F1.8 GM. Yet despite its large aperture, it’s not wildly expensive: it costs £1,400, compared to £1,300 for the Sony f/1.8 lens.
There are a couple of reasons other brands don’t make a lens this wide with such a fast maximum aperture. Firstly, they are hard to make well. Secondly, with the sort of depth-of-field you get with a 14mm lens, f/2.8 has usually been seen as a large enough opening. Sigma though is aiming this ultra-wideangle optic at night-sky shooters who need to carefully balance their shutter speeds with their ISO settings, so a super-fast maximum aperture makes life very much easier. Indeed, the firm has gone to quite some lengths with its other features to keep the astrophotography crowd happy.
Features With its 114.2-degree angle of view, this lens offers an extremely wide view, which makes it ideal for recording small spaces and open landscapes, as well as vast expanses of the night sky. It’s distinctly large and heavy when compared to other 14mm lenses, at 15cm long and 1,170g.
However, Sigma is very proud that this is almost exactly the same size and weight as its previous 14mm f/1.8 that was designed for DSLRs. This new model lets in two-thirds of a stop Panasonic Lumix S5II, 30min at f/1.4, ISO 800 more light, so maintaining the same dimensions has been quite an achievement. That the lens has been specifically designed for mirrorless bodies helps, of course, as the distance to the sensor is shorter.
Sigma has used an optical design containing 19 elements in 15 groups, including four aspheric elements, three made from FLD glass and one from SLD glass to help tackle chromatic aberrations. The aspheric lenses are important here, as we need the edges of the frame to be as sharp and detailed as the centre. In astrophotography, we often need to look at subjects that aren’t in the middle of the frame.
Now we have excellent software for fixing basic problems with optics, Sigma has taken the decision to leave the final correction of geometric distortion and vignetting to the in-camera firmware and software profiles. This allows it to concentrate on the things software can’t fix,
