Sigma 20mm F1.4 DG HSM Review

November 19, 2015 | Mark Goldstein | |

Introduction

The Sigma 20mm F1.4 DG HSM is the world’s first f/1.4 ultra-wide-angle prime lens for full-frame and APS-C DSLR cameras. It offers the equivalent angle of view as a 30mm lens on an APS-C system (depending on the crop factor). The Sigma 20mm F1.4 DG HSM is comprised of 15 elements in 11 groups, including two FLD (“F” Low Dispersion)* glass and five SLD (Special Low Dispersion) glass elements to minimise transverse chromatic aberration, and it features a rounded 9 blade diaphragm which creates an attractive blur to the out of focus areas of the image. It has a minimum focusing distance of 27.6cm / 10.1in and a maximum reproduction ratio of 1:7.1. The Sigma 20mm F1.4 DG HSM is the fifth lens in the growing Art line (the other ranges are Contemporary and Sports). The Sigma 20mm F1.4 DG HSM lens is currently available for £849.99 / $999.99 in the UK and the US, respectively.

Ease of Use

Sigma 20mm F1.4 DG HSMThe Sigma 20mm F1.4 DG HSM lens mounted on a Canon EOS 5DS R

Weighing in at 950 grams and measuring 13cm in length, the Sigma 20mm F1.4 DG HSM is certainly a big, heavy lens given its focal length. As seen in the photos below, it complements a full-frame camera like the Canon EOS 5DS R better than on a smaller APS-C camera.

Sigma 20mm F1.4 DG HSMThe Sigma 20mm F1.4 DG HSM lens mounted on a Canon EOS 5DS R

Sigma 20mm F1.4 DG HSMThe Sigma 20mm F1.4 DG HSM lens mounted on a Canon EOS 5DS R

Sigma 20mm F1.4 DG HSMThe Sigma 20mm F1.4 DG HSM lens alongside a Canon EOS 5DS R

Build quality is excellent. The lens has a plastic shell with a mixture of metallic parts and a new compound material, TSC (Thermally Stable Composite), used inside. It also incorporates a brass bayonet mount that's supposed to be more durable. The optical elements are made of high-grade glass. The focus ring is pleasingly wide and ridged for easier grip.

Sigma 20mm F1.4 DG HSMSide of the Sigma 20mm F1.4 DG HSM lens

Sigma 20mm F1.4 DG HSMSide of the Sigma 20mm F1.4 DG HSM lens

In terms of features, the Sigma 20mm F1.4 DG HSM offers all the basics that you need from a prime lens. The main exception is the lack of built-in Vibration Reduction, although the very fast maximum aperture of f/1.4 makes up for this.

Sigma 20mm F1.4 DG HSMFront of the Sigma 20mm F1.4 DG HSM lens

Sigma 20mm F1.4 DG HSMRear of the Sigma 20mm F1.4 DG HSM lens

Focusing is usefully internal and manual focusing is possible when set via the Focus switch on the lens barrel. Full-time manual focus override is also available at any time simply by rotating the focus ring.

A clear distance scale in both feet and meters runs from the closest focusing distance of 0.276m / 0.82 ft to infinity.

Sigma 20mm F1.4 DG HSMFront of the Sigma 20mm F1.4 DG HSM lens

Sigma 20mm F1.4 DG HSMRear of the Sigma 20mm F1.4 DG HSM lens

The Sigma 20mm F1.4 DG HSM ships with a good quality soft case, a fixed plastic petal-shaped lens hood and a large round lens cap. A metal lens cap is also available (LC907-02, sold separately).

Note that this lens doesn't accept standard screw-on circular filters thanks to its large, bulbous front element.

Sigma 20mm F1.4 DG HSMThe Sigma 20mm F1.4 DG HSM lens in-hand

Sigma 20mm F1.4 DG HSMFront of the Sigma 20mm F1.4 DG HSM lens, with the supplied lens cap fitted

Focal Range

At the 20mm focal length the angle of view is 94.5 degrees.

 Sigma 20mm F1.4 DG HSMField of view at 20mm

Focusing

The Sigma 20mm F1.4 DG HSM lens has a wide focus ring. There are hard stops at both ends of the range, making it easier to set focus at infinity.

When it comes to auto-focusing, the Sigma 20mm F1.4 DG HSM zoom is a quick performer, taking about 0.15 seconds to lock onto the subject when mounted on the Canon EOS 5DS R that we tested it with.

We didn't experience much "hunting", either in good or bad light, with the lens accurately focusing almost all of the time. It's also a very quiet performer, thanks to the built-in HSM (Hyper Sonic Motor), which makes this lens well-suited to video recording.

Chromatic Aberrations

Chromatic aberrations, typically seen as purple or blue fringes along contrasty edges, is well-ontrolled but can be detected in some shots, as shown below.

Sigma 20mm F1.4 DG HSM Sigma 20mm F1.4 DG HSM
   
Sigma 20mm F1.4 DG HSM Sigma 20mm F1.4 DG HSM

Light Fall-off

With the lens set to its maximum aperture of f/1.4, there is very significant light fall-off in the corners. Stopping-down to f/4 virtually eliminates this.

Sigma 20mm F1.4 DG HSMLight fall-off

Macro

The Sigma 20mm F1.4 DG HSM isn't claimed to be a macro lens, with a minimum focusing distance of 27.6 cm / 10.9 in. and a maximum magnification ratio of 1:7.1. The following example demonstrates how close you can get to your subject, in this case a Compact Flash memory card.

Sigma 20mm F1.4 DG HSMClose-up performance

Bokeh

Bokeh is a word used for the out-of-focus areas of a photograph, and is usually described in qualitative terms, such as smooth / creamy / harsh etc. In the Sigma 20mm F1.4 DG HSM lens, Sigma have employed an iris diaphragm with nine rounded blades, which has resulted in nice bokeh in our view. We do realise, however, that bokeh evaluation is subjective, so we've included several 100% crops for your perusal.

Sigma 20mm F1.4 DG HSM Sigma 20mm F1.4 DG HSM
   
Sigma 20mm F1.4 DG HSM Sigma 20mm F1.4 DG HSM

Sharpness

In order to show you how sharp this lens is, we are providing 100% crops on the following page.

Entry Tags

review, samples, photos, test, images, sample images, jpeg, wide-angle, preview, jpg, DSLR, prime, sigma, DSLR camera, wide, 20mm, 1.4, ultra-wide-angle, Sigma 20mm F1.4 DG HSM A