The Nikon 20 mm f/1.8G ED AF-S appeared in the middle of 2014, at the same time as the Nikon D750. Do you need a bright lens, now that cameras have an increasingly higher signal-to-noise ratio? What is the use of an FX format lens with a large aperture and a fixed focal distance of 20 mm when using a Nikon DX-format SLR camera? High sharpness with a versatile field of view, beautiful background blur, lower ISO values with which you can work longer without a flash and tripod, coupled with nice ergonomics and high image quality. That is what the Nikon 20 mm f/1.8G has to offer.

Street photography? Nikon 20 mm f/1.8G ED AF-S

Construction and auto focus

The Nikon 20 mm f/1.8 is reasonably compact and weights 350 grams. With an SLR camera, it makes a combination that isn’t too heavy and lies well in the hand. The construction is, as we’re accustomed to from the Nikon f/1.8G-series lenses, high-quality and solid, whereby the application of high-quality plastics keeps the weight at a reasonable level. There’s 1 switch on the lens, for AF/MF. Built-in image stabilization is lacking. You won’t often miss it, but with image stabilization, this lens would be even more attractive (and somewhat more expensive).

The shortest focal distance is 20 cm, and that ensures—in combination with the short focal length—that you can get very close to a subject and yet get a lot in frame.

Vignetting Nikon 20 mm f/1.8G

The Nikon 20 mm f/1.8G is designed for use on a camera with a full-format/FX sensor. If you use such a lens on a camera with a smaller DX sensor, such as our Nikon D7100 test camera, then you have practically no trouble with visible vignetting with in-camera jpg files and the brightness correction on Normal. At full aperture, you see 1 stop of vignetting in the RAW files, but that’s also already gone after stopping down 1 stop.

Bilbao, Nikon 20 mm f/1.8G + Nikon D7100 @ 100 ISO, f/4, 1/30 sec

Distortion Nikon 20 mm f/1.8G

For a lens with a short focal length, the distortion is very low, although you can recognize a bit of barrel-shaped distortion in shots not corrected for distortion. Our experience is that the Nikon lens correction profiles in Lightroom and Photoshop lead to even better results, without too much loss of resolution. We haven’t tested this, because at the time of the review, the correction profile for the Nikon 20 mm f/1.8G was not yet available.

Flare

The lens design consists of 13 lens elements, of which 2 are made of high-quality ED glass and two are aspherical elements, all sorted into 11 groups. With so much glass in a lens with a short focal length, there is always a chance of internal reflections. The included flower-shaped sun cap and the application of Nano Coat on the individual lens elements ensure the minimization of this. Even so, the chance is good that when there’s a bright light source shining directly into the lens if you’re taking a picture in the dark, that green ghosts will appear in the image.  

Sharpness

Already at full aperture, the Nikon 20 mm f/1.8G delivers a sharp image. The impression of sharpness is also strengthened by the—for a wide-angle lens—beautiful background blur/bokeh, which you have partly as a result of the high brightness. At f/4, the highest sharpness will be reached, and it decreases starting at f/11 as a result of diffraction. Point light sources at the edges of the image will be reproduced with minimal comet-shaped light flecks (coma) on a camera with a DX sensor, thanks to a modern lens design.

In order to photograph without flash or tripod in a dark church, you need not only a high ISO, but also a large aperture in order to achieve a shutter speed of 1/300.
Bilbao, Nikon 20 mm f/1.8G + Nikon D7100 @ 6400 ISO, f/1.8, 1/30 sec

Chromatic aberration

Bokeh

Lenses with a short focal length deliver a big focal depth, so that you can less easily play with the background blur/bokeh, than with telephoto lenses. Thanks to the high f/1.8 brightness, you can make the focal depth relatively small with the Nikon 20 mm f/1.8G. But focal depth is not the only factor that influences the bokeh: the lens design also contributes.

Conclusion Nikon 20 mm f/1.8G ED AF-S with Nikon D7100

See our list of tested lenses or the lenses with a Nikon mount tested by us to compare the performance of this lens to 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”.

Pros

• Good image quality, particularly at f/5.6
• High brightness and yet compact and light
• Short focal length with little distortion
• Fast and silent internal AF
• Broadly usable focal point on DX

Cons

• Sensitive to flare
• No built-in image stabilization

Do you buy a new camera or a bright lens, if you want to have less noise?

Modern Nikon SLR cameras with a DX sensor have such a high signal-to-noise ratio that investing in a modern camera leads to an improvement of the signal-to-noise ratio by a third or half a stop. An investment in a modern, bright lens like the Nikon 20 mm f/1.8 not only gives you more than 1 stop profit in signal-to-noise ratio, it also delivers a brighter viewfinder image and sharp pictures. The exceptionally high brightness also gives you the ability to play a bit with background blur/bokeh. Couple that with a field of view that corresponds with 30 mm in 35-mm equivalent, and it’s clear that the Nikon 20 mm f/1.8G is a bonus for every Nikon fan with a DX SLR.