Nikon AF-S Nikkor 20mm f/1.8G ED Lens Review

Nikon AF-S Nikkor 20mm f/1.8G ED Performance

At f/1.8, sharpness in the centre of the frame is good, although performance towards the edges is only fairly good. Stopping down improves clarity across the frame, peaking between f/4 and f/5.6. Here sharpness is outstanding in the centre, and approaching excellent levels towards the edges of the frame.

MTF

How to read our charts

The blue column represents readings from the centre of the picture frame at the various apertures and the green is from the edges. Averaging them out gives the red weighted column.

The scale on the left side is an indication of actual image resolution. The taller the column, the better the lens performance. Simple.

For this review, the lens was tested on a Nikon D600 using Imatest.

Levels of chromatic aberrations are kept within acceptable levels, remaining just below one pixel width at maximum aperture. This level of fringing should be difficult to spot, even in large prints, and harsh crops from the edges of the frame.

CA

How to read our charts

Chromatic aberration is the lens' inability to focus on the sensor or film all colours of visible light at the same point. Severe chromatic aberration gives a noticeable fringing or a halo effect around sharp edges within the picture. It can be cured in software.

Apochromatic lenses have special lens elements (aspheric, extra-low dispersion etc) to minimize the problem, hence they usually cost more.

For this review, the lens was tested on a Nikon D600 using Imatest.

Falloff of illumination towards the corners is quite severe. At maximum aperture the corners are 3.29 stops darker than the image centre and visually uniform illumination isn't achieved until stopped down to f/5.6 or beyond.

Imatest managed to detect 1.42% barrel distortion, which is a reasonably mild amount of distortion , especially for a 20mm lens. If straight lines are of the utmost importance, you'll be glad to hear that the distortion pattern is uniform across the frame, which should make applying corrections in image editing software afterwards relatively straightforward.

Thanks to Nikon's Nano Crystal optical coating, the lens is very resistant to flare and contrast holds up well when shooting into the light. A petal shaped hood is supplied as standard, which does a sterling job of shielding the lens from extraneous light, that may cause issues.

Value For Money

Priced at around £680, this lens represents reasonable value for money, especially given its ultra-wide angle of view and fast f/1.8 maximum aperture.

Those with an eye for a bargain may consider this lens' predecessor. The old Nikon 20mm f/2.8D does have a slower maximum aperture, and lacks silent focusing, but it can be picked up for around £460.

Sigma also produce a 20mm f/1.8 lens for Nikon cameras. Their 20mm f/1.8 EX DG Aspherical lens lacks silent focusing, but only costs £390. however, it does have a reputation for producing a 'dreamy', soft look on images taken at maximum aperture.

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