Review Sigma 20 mm f/1,4 Art
Focus to 7 meters’ distance at 20 mm. At f/1.8, the focal depth is from 3.5 meters to infinity. At f/1.4, the focal depth is “only” 28 meters (from 4 to 32 meters). That makes a difference in the bokeh.
After Sigma broke records for the world’s brightest zoom lens with the Sigma 18-35mm f/1.8 Art (for cameras with APS-C/DX sensors) and the Sigma 24-35mm f/2 (for cameras with a full-frame/FX sensor), it is now the turn of a Sigma lens with a fixed focal length to break world records: the world’s first 20 mm f/1.4 ultra-wide-angle lens for cameras with a full-frame sensor. This is a fantastically bright lens that offers sensational new creative options. If you want, on a camera with a full-frame sensor, to be able to play with the background blur/bokeh using a wide-angle lens with a focal length of 24 mm, or in this case even less, then you need a very bright lens. A very bright lens. The focal depth even at f/2.8 is already really big if you use a lens with a 20 mm focal length. The choice between bokeh and focal depth, linked to an extremely bright wide-angle lens, makes this new world-record holder attractive to many people. Perhaps a “must.”
|How you make a wide panoramic shot of a small street with a 20 mm lens: practice shot Sigma 20 mm f/1.4 Art with Nikon D810 @ f/2, 400 ISO, 1/500 sec|
Sigma deals in world records, now at fixed focal lengths as well
Sigma 20 mm f/1.4 Art: designed for ultra-high megapixel sensors
The complex lens design and the weight of this lens betray the fact that Sigma has set the bar very high for themselves: various high-quality glass elements of FLD and SLD glass (expensive glass types with high density, good color reproduction and low chromatic aberration) are used. There are also two aspherical elements applied, including an extremely challenging precise large one (59 mm, necessary due to the high brightness in combination with the big field of view). This aspherical lens element is marked in red on the left-hand side of the lens design. Sigma claims that this advanced design ensures a minimum of distortion, lateral chromatic aberration, "sagittal coma flare" (important for starry skies, so that the stars are shown as points), and vignetting.
Build and auto focus
The build quality of the Sigma Art series is now renowned. It is among the best there is for sale. The only thing that remains to be desired is complete protection against dust and splashwater. The combination of a short focal length and extremely high brightness means that you will not need image stabilization under just about every lighting condition. The heavy metal mount ensures a connection to the camera that is free of play, which is important for cameras with high pixel counts. You do not have to worry about forgetting the lens hood, or losing it, since, as with most ultra-wide-angle lenses, it is secured to the lens. It means that you cannot screw any traditional filters to this lens and that you get a special lens cap with it that only fits this lens.
Vignetting, flare and distortion Sigma 20 mm f/1.4 Art
Vignetting is a common phenomenon for cameras with a full-frame sensor. And especially with wide-angle lenses. But not with Sigma. At full aperture, the vignetting of the Sigma 20 mm f/1.4 Art on a Nikon D810 is one and a half stops. At f/2.8, the vignetting is as good as invisible. Sensationally good for a 20 mm lens.
Distortion is another Achilles heel for wide-angle lenses. You can combat vignetting by choosing a smaller aperture, but only a smaller sensor or software correction helps with distortion. The Sigma 20 mm f/1.4 Art already has remarkably little trouble with distortion even without software correction. Less than 1.5% barrel-shaped distortion is not something you will often have to correct with software. My compliments for this performance to the designers from Sigma.
Of course ghosts and flare are not entirely absent 100% of the time. That probably isn’t possible with a big, convex front lens element and a colossal field of view. Even so, the Sigma 20 mm f/1.4 Art, just like all other Sigma Art lenses, has strikingly little trouble from flare and ghosts in comparison with similar lenses from the competition. That is not only thanks to Sigma's Super Multi-Layer Coating and the flower-shaped lens hood that you will never forget since it’s attached to the lens. There’s more; otherwise it would not be possible to have so little trouble from flare with an extremely short focal length.
The first thing that stands out when reviewing shots made at full aperture is the high center sharpness of this bright lens. At f/4, the highest center sharpness is reached, but the difference from f/1.4 is something that you will only see with very big enlargements. It is also striking how close the sharpness at the edges comes to the center sharpness. As can be expected for this kind of lens, the sharpness in the corners is lower. If you really want everything sharp from corner to corner, then it pays to stop down. But otherwise, you are free to choose the aperture that you want: the image quality is always good. Playing with the bokeh/background blur of a wide-angle lens where the center sharpness is already good from full aperture (Click on the image shown here.)—it’s a unique experience.
When light passes through a glass lens, you run the risk that the different colors will be separated from each other, with the result that you can encounter colored edges at sharp contrast transitions in the corners (“lateral chromatic aberration”). This is kept beautifully in check with the Sigma 20 mm f/1.4 Art. FLD glass has many properties that correspond with the extremely expensive Fluorite glass, including extremely little chromatic aberration. Because it is precisely wide-angle lenses (and telephoto lenses) that are sensitive to chromatic aberration, these glass types are the ones used.
Bokeh Sigma 20 mm f/1.4 Art
It is not only the quality of the (in particular, aspherical) lens elements that ensure a quiet bokeh. The aperture, with 9 rounded lamellae, also makes a contribution.
Optional USB dock
|All Sigma Art, Contemporary and Sports lenses can, thanks to the optional USB dock, get new firmware installed by the user. The auto focus performance and various user options can also be tweaked with the USB dock. In the demo video above, Sigma shows how you install a lens firmware update for a Sigma lens with the USB dock. |
Fashionable metal lens cap
|Optionally, there is an even nicer, metal lens cap (LC907-02) for sale by Sigma, with material that matches the high-quality finish of the lens. You will not take better pictures with it. Specialty lens caps are not sold in great numbers, and they are never cheap. Even so, I have a weakness for more luxurious lens caps. I cannot explain why, really, but I almost always buy them. |
Conclusion Sigma 20 mm f/2 Art review with Nikon D810
Use the Lens Comparison or look in our list of reviewed lenses to compare this lens with other lenses.