The Nikon 20 mm f/1.8G is an unusual lens. First, there are few bright(<f/2) wide-angle lenses, especially for cameras with an FX-format sensor. Second, the field of view is enormous: with an ultra-wide-angle lens, you exaggerate the perspective and show the breadth of a space, even if it isn't all that big in reality. In addition, a bright lens also provides a bright viewfinder image, which, for example, is nice for interior photography. With a suggested retail price of less than 800 euros at its introduction in September 2014, including lens bag and sun cap, this seems to be a very attractive lens.
The lens design consists of 13 lenses in 11 groups, including two aspherical and two extra-low dispersion lens elements, which help to limit color shifts and spherical lens errors. A 77 mm filter size gives this lens, seen from the front, a more impressive appearance than the other f/1.8 lenses that I mentioned earlier. The lens mount is made of metal, but in order to keep the weight and the price as low as possible, the lens housing is made of plastic. Some professional photographers, who are used to the more expensive Nikon lenses may find that unfortunate, because this combination of focal length and brightness is also interesting for them. The lens weighs just 350 grams, and that's terrifically light for an FX wide-angle lens.
Focusing is fast and quiet. Thanks to an internal focus mechanism, the front lens does not turn when focusing, which is handy when using filters. A ultra-wide angle with a shortest focal distance of 20 cm provides a lot of enjoyment when you capture subjects from so close up.
During the review, we made use for the jpg files of the ability to correct for vignetting. Those who photograph in jpg will have no trouble with vignetting, and that is very nice for an ultra-wide angle on FX. In particular at full aperture, the vignetting is clearly visible when you're working in RAW. That is usual for this kind of lens, and it is simple to correct with software.
A bright, ultra-wide angle is ideal for photos and videos of interiors, street documentaries, broad landscapes and underwater photography.
In the jpg files that are stored in the camera, the distortion is too beautiful to be real for an ultra-wide angle. There was also correction for distortion in our test camera. But even in the uncorrected RAW files, the barrel-shaped distortion, visible at 2%, is still remarkably low for an ultra-wide angle.
Sensitivity to backlighting is usually an Achilles' heel for ultra-wide-angle lenses. The Nikon 20 mm f/1.8G doesn't completely escape from it either. The lens elements of the Nikon 20 mm f/1.8 is equipped with Nano Crystal coating in order to combat internal reflections. Even so, with direct backlighting, you can get considerable flare and ghosts. The 7 rounded lamellae ensure in this case a beautiful star around the sun.
Sharpness Nikon 20 mm f/1.8G ED AF-S
This Nikon ultra-wide angle provides sharp, bright images with good contrast.
The center sharpness of the Nikon 20 mm f/1.8G on a camera with an FX sensor (Nikon D810) is already very good at full aperture, and it remains that way through an aperture of 11. In contrast with the other Nikon f/1.8 lenses, this ultra-wide angle scores a little lower for image quality in the corners, but given the extreme focal length, that's no surprise. The sharpness on the edges and in the corners does increase as you stop down. For the RAW files without sharpening (move your mouse over the picture), the center sharpness is already at maximum at full aperture, which is a compliment for Nikon's designers.
If you photograph with a Nikon camera and you save the photos as jpg, then you never have to worry about lateral chromatic aberration (purple and green edges at sharp contrast transitions in the corners of the image). This is perfectly corrected, without you having to check on it as the photographer. In RAW, the lateral chromatic aberration is sometimes visible, but it is remarkably little for an ultra-wide-angle zoom.
The bokeh looks reasonably even, with an onion-ring pattern sometimes visible as a result of the aspherical lenses. A bright lens with an aperture of f/1.8 usually delivers images with a small focal depth and a beautiful, flowing bokeh. Don't expect miracles in this case when it comes to the limits of the focal depth, because a lens with an extremely low focal length almost always delivers a lot of focal depth. For most applications, that will be a pleasant plus point. For isolating a subject during street photography, I would choose a longer focal length.
Conclusion Nikon 20 mm f/1.8G ED AF-S with Nikon D810s
Look in our list of reviewed lenses or the lenses we've reviewed with a Nikon mount in order to compare the performance of this lens with that of other lenses.
WYSIWYG score: This table shows the performance of this lens if you save the files in the camera as jpg, with all available in-camera lens corrections applied. This score gives you for this lens/test camera combination: "What you see is what you get".
Pure RAW score: DThis table shows the performance of this lens if the file is stored in the camera in RAW format.
Good built and image quality (high center sharpness!)
Fast and silent AF
Little distortion for an ultra-wide angle
Compact and light
Visible chromatic aberration in the corners (in RAW)
Sensitive to backlighting
The Nikon 20 mm f/1.8G is a logical and welcome supplement to the 85 mm, 50 mm, 35 mm and 28 mm f/1.8 series. A bright, ultra-wide angle with the build and image quality that this lens offers is ideal for photos and videos of interiors, street documentaries, broad landscapes and underwater photography. In contrast with the other Nikon Nikon f/1.8 lenses, this ultra-wide angle scores a bit lower for the image quality in the corners, but that is, given the extreme focal length, no surprise. The very high center sharpness, the compact dimensions and the low weight mean that you'll love taking a Nikon 20 mm f/1.8G along with a Nikon D810 or another FX camera on a photography excursion.
Author: Ivo Freriks
With Camera Review Stuff I hope to make a modest contribution to the pleasure that you get from photography. By testing cameras and lenses in the same way, evluating the results and weighing up the pros and cons, I hope to help you find the right camera or lens.