The world’s first f/1.4 20mm optic is in line with Sigma’s reputation of innovation in paths where others have not treaded. Right from manufacturing the widest full frame zoom, to making the fastest zoom lenses for both DX and FX, the company has been at the forefront of design breakthroughs that tend to make a lens unique, even before one analyses and evaluates it on the test bench. |
| Sigma 20mm f/1.4 DG HSM Art for Canon |
Features
Sigma says they have made use of advanced large-diameter aspherical lens manufacturing technology to design this lens, also minimising distortion, transverse chromatic aberration, sagittal coma fl are and vignetting. Ordinarily, a 9-bladed diaphragm may not have seemed important in a 20mm lens, but considering its aperture, one can actually blur out the background quite effectly, if you go really up close!
Handling
There is a substantial amount of metal that has gone into this robust construction, but it’s disappointing to see another Art series lens that is not weathersealed. Even the plastic-body, much lighter Nikkor 20mm f/1.8 has partial weathersealing, with a rubberised gasket around the mount that the Sigma omits. That said, it’s interesting to note that the lens has been constructed using Thermally Stable Composite material for greater precision in wide temperature variations.
Owing to the lens’ bulbous front element, one cannot use fi lters, which is a serious drawback. In the future, one may be able to use third-party solutions like the ones created for the Nikkor 14–24mm (which has a similar front element), but these contraptions are bulky and expensive.
Manual focus users may find the rotation required for the focusing ring to go from minimum focusing distance to infinity a little short. While that is still quite workable, I was disappointed to see distance markings only for f/8 and f/16. Zeiss tends to spoil us, perhaps. Most crucially, the company touts this lens as a serious astrophotography tool, but the lack of an infinity hard stop seems a little contradictory.
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| The 20mm exhibits excellent control over distortion, and holds its quality well despite diffraction after f/11. Exposure: 1/50sec at f/16 (ISO 800) |
Performance
The Sigma’s resolving power, wide open, at the centre, is outstanding. It is almost as sharp as the new 21mm optics by Zeiss, and that’s despite being a stop (versus the Milvus) or two (versus the Loxia) faster. Corners are a little smeared, but if you are shooting at f/1.4 on a 20mm lens, your subject is not going to be anywhere near the corners.
Stop down to f/4 and f/5.6 and the lens is near flawless, with edge-to-edge crispness. Chromatic aberration is well controlled. The built-in lens hood does a good job in keeping stray light away. The control over vignetting is admirable, considering that this has been the Achilles heel of some of the other Sigma Art optics. On the Canon 6D, the autofocus is relatively quick. One can expect it to be faster, of course, on other bodies like the Canon 5D Mark III, 5DS R, 1D X or the Nikon D750, D810, D4S.
Conclusion
There is no doubt that the Sigma 20mm f/1.4 Art is an astonishing piece of optics. Unfortunately, it alienates a chunk of its otherwise potential audience because of its inability to use filters. So if you are a landscape photographer, or shoot a lot of daytime video that necessitates ND filters, you may want to look at the Nikkor 20mm f/1.8G and the Zeiss Milvus 21mm f/2.8. The Milvus, also tested in this issue, is a different beast, and is a clear winner in terms of build quality and on-field handling.
But low light shooters would crave AF, and thus remain two significant reasons to buy the Sigma 20mm f/1.4 Art. One, if you really need that extra two-thirds stop over the Nikkor 20mm f/1.8... wedding photographers may look at this keenly. Two, if you can forgo filters in order to use the pinnacle of ultrawide optics amongst autofocus lenses.
FINAL RATINGS
Features
World’s fastest 20mm, compatible with USB dock, two FLD elements, five SLD elements. 19/20
World’s fastest 20mm, compatible with USB dock, two FLD elements, five SLD elements. 19/20
Performance
Excellent centre-to-edge sharpness, good control over flare, very minimal distortion. 34/35
Build Quality
Sturdy barrel, no weathersealing. 23/25
Ergonomics
Small focus throw, smooth, dampened focus ring, inability to use filters. 12/15
Warranty & Support
Two-year warranty with service centres in major metropolitan cities. 3/5
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