Sigma 20mm F1.4 Art criticism: More than a landscape lens
"Not everyone loves wide-angle lenses, but Sigma's 20mm art made me a fan."
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Rare combination of focal length and aperture
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Impressively sharp at 1: 1.4
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Professional build quality
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Good price
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Strong vignetting
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No filter support
Wide-angle lenses are not sufficiently recognized for their versatility. If you think they are only for landscapes, give me the opportunity to change your mind. Although it's a landscape and astrophotography lens, I enjoyed using the Sigma 20mm F1.4 Art for portraits and product photos, and it was the perfect lens for wedding party dance shots (don't worry, that was a couple of months ago before, before social distancing).
This is not a new product – Sigma released it in 2015 – but when I got one borrowed for my Nikon D780 review, I liked it so much that I thought I should write it down. At 5 years old, this $ 900 lens is still the current champion in fast wide-angle prime numbers for Nikon and Canon DSLRs. It is also available for mirrorless Leica L or Sony E mounts, although it is a little more difficult to recommend for such cameras.
The design of the 20mm artwork raises some usability concerns that I will discuss later. However, if you're looking for the ultimate in low-light performance, no other 20mm lens is comparable to this. Considering the price to compete with the two 20mm f / 1.8 first-party lenses, this is an excellent buy.
design
Every photographic lens is a compromise exercise. Price, size, image quality and functions must be balanced to achieve a goal. With the Sigma Art series, it has always been important to deliver the best quality at a price that exceeds, or at least does not exceed, that of equivalent first-party lenses – regardless of size.
Weighing over 2 pounds, the 20mm art is certainly not a lightweight, but that's the price you pay for a 1: 1.4 bright aperture and an excellent optical formula. The 15 elements in 11 groups, including two aspherical elements, two of the “F” dispersion elements from Sigma and five special low dispersion elements, ensure sharp, aberration-free images with minimal distortion.
The lens body measures 3.6 inches in diameter and 5.1 inches long, including a built-in petal-style lens hood. I thought it would go well with the Nikon D780, but I'm not sure how to use it with a mirrorless camera.
This is a DSLR first lens. The mirrorless version includes an integrated "adapter" to compensate for the difference in the distance between the flange and residue, which makes the lens longer. Perhaps this wouldn't feel too out of place with a powerful Panasonic S-series camera, but I don't know how comfortable it would be with a smaller, lighter Sony Alpha-series camera. Given that Sony recently launched the excellent FE 20mm f / 1.8G, there's a solid alternative for E-mount shooters.
The Sigma offers a minimalist exterior with a wide, knurled focus ring and a window removal scale that give it a first-class appearance. The AF / MF switch is the only other control point. There is neither a stabilizer to turn on or off – not that I would expect with a lens so wide and fast – nor an aperture click switch like the one we see on Sony's 20mm f / 1.8 and Sigma's own 35 mm saw F1. 2 Art.
The bulbous front element of the Sigma means that you cannot use a standard screw-on filter. This can be a problem for landscapes if you want a polarizer or neutral filter. Professionals and other seasoned shooters may not mind using a filter adapter with large drop-in filters, but for the rest of us, the lack of native filter support could be a reason to consider an alternative lens.
Autofocus
With the Hyper Sonic Motor (HSM) from Sigma, the 20 mm F1.4 graphics can be quickly focused in the viewfinder as well as in the live view. If you switch from the foreground to the background, you can feel the torque of the motor when it is switched on. Still, it makes very little noise.
Continuous autofocus performance was also very good – no doubt supported by the intelligent focusing algorithm used in the D780 – and kept pace with a cyclist heading towards me. It was also decent in a dimly lit lobby, although the camera's focus sensor was probably the bigger limiter (the D780 is good for -3 EV with the viewfinder).
However, there is a big problem with autofocus, at least when shooting through an optical viewfinder. After unpacking, my copy of the lens was focused pretty dramatically. Customers have reported similar issues in user reviews. This isn't exactly new to Sigma – I also found the problem when reviewing the 105mm F1.4 art – but it seems to be something the company is using with newer lenses like the 40mm art, which I have now recorded seems to be under control on Canon and Nikon with no problems.
Fortunately, most modern DSLRs offer the ability to adjust the focus behavior of a lens (the Nikon D780 can do this automatically using the AF fine-tuning feature that uses focus information from live view to correct viewfinder performance). You can also purchase the Sigma USB lens dock to program focus settings directly into the lens firmware.
While this problem is easy to fix, the customer must know how to recognize it. I can imagine someone buying and returning this lens because they just thought it wasn't sharp. That couldn't be further from the truth.
picture quality
When I realized what was happening with the autofocus and figured out how to fix it, the Sigma 20mm Art thrilled me with incredibly detailed images and surprisingly rich bokeh (which is usually not the case with such wide lenses). There seems to be little to no sacrifice in sharpness when opened wide at 1: 1.4.
Distortions are certainly there, but they are fairly mild and can be easily corrected in the post without much harvest.
However, vignetting could be the real problem here, especially if you want to use this lens for astrophotography. Photography in the night sky usually requires a bright aperture and even focus and exposure across the frame. At 1: 1.4, the 20mm type vignettes are exactly what you would expect from a 20mm 1: 1.4 lens. It is serious.
I don't mind that with other types of photography, but with astrophotography, if you are already shooting at high ISO values, correcting the vignette in the post by lightening the corners only leads to more noise. Maybe it's not a big deal – I've seen fantastic astro shots from other photographers who used this lens – but it's something to watch out for.
Our opinion
The 20mm focal length may be of limited use to most photographers, but the Sigma 20mm F1.4 Art has made me a fan. I really enjoyed taking pictures with it, much more than I thought, especially for subjects that don't expect a lens as wide as portraits and products. Sometimes a new perspective is enough to refresh your creativity. Literally.
As an older model, the 20mm art has shown Sigma to improve auto focus accuracy on newer lenses. I would love to see a mirrorless redesign of this lens, as Sigma did for the 14-24mm f / 2.8 type. For Canon and Nikon DSLR shooters, however, this is still the wide-angle prime to beat.
Is there a better alternative?
Certainly not for Canon DSLRs. Nikon manufactures a 20mm f / 1.8 that is significantly lighter (12oz) and accepts 77mm filters. It's also quite a bit cheaper at the time of this writing, thanks to instant discounts that get it to just under $ 720. However, the sigma is sharper and brighter, and I expect the additional $ 180 to be worth it.
For Sony shooters, the FE 20 mm 1: 1.8 G is worth a look. It weighs just over 13 ounces, uses 67mm filters, and has an aperture ring with de-click controls. It is also visually excellent. At $ 900, however, you save no money and sacrifice the additional 2/3 blink collection that the f / 1.4 aperture of the Sigma offers you. For most people, however, this is a worthy trade for a lens that better fits Sony's smaller cameras.
How long it will take?
The 20mm art that was released in late 2015 is 5 years old and remains one of the best wide angles on the market. I wouldn't be surprised if Sigma introduces a mirrorless version in the not too distant future, but anyone who buys this lens for a DSLR today should have no problem working with it for many years.
Should you buy it
If you record a Canon or Nikon DSLR, absolutely. If you're shooting a mirrorless L-mount camera, maybe. If you're shooting a Sony E-mount camera, this is probably not the case – choose the FE 20mm f / 1.8 from Sony.
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