The Nikon AF-S Nikkor 20mm f/1.8G ED ($799.95) is just one of many in the company's series of f/1.8 prime lenses. It's the widest of the bunch, but even when shot at its maximum aperture it is quite sharp in the center. Landscape shooters will want to stop down for edge-to-edge crispness, and the lack of image stabilization is really only a concern when recording handheld video. The lens is a solid performer, and a good choice for any Nikon shooter that wants an ultra-wide-angle prime lens. It can be used with both full-frame and APS-C Nikon cameras.

The 20mm ($716.95 at Amazon)  measures in at 3.1 by 3.2 inches (HD), weighs just 12.6 ounces, and uses large 77mm front filters. It can focus as close as 7.8 inches, which certainly doesn't qualify it as a macro lens, but does let you get up close and personal with subjects. When combined with the wide aperture, that allows for a very shallow depth of field. The only control switch on the lens toggles between manual and autofocus control; there's a large, ridged ring for manual focus adjustment. The lens barrel is a hard plastic, in black with gold accents, and the lens mount is metal.

I used Imatest to check the sharpness of the lens when paired with the full-frame D750 ($1,496.95 at Amazon) . At f/1.8 it does better than the 1,800 lines per picture height we like to see from a lens, scoring 1,903 lines on our center-weighted sharpness test. Image quality holds up through most of the frame, but the outer third is soft, showing just 1,326 lines.

Stopping down to f/2.8 improves the overall sharpness to 2,279 lines, but edges are still on the soft side at 1,612 lines. The lens is just about the same at f/4, but at f/5.6 both its center-weighted score (2,548 lines) and edges (2,124 lines) are better. There's another modest increase in sharpness at f/8, and at f/11 diffraction sets in and starts to hurt performance, but even there it's still 2,575 lines. There's a modest amount of barrel distortion, about 1.1 percent, which is just barely noticeable in field conditions. That's not out of line for a lens with this wide of a field of view.

If you love to capture images at wide angles, the Nikon AF-S Nikkor 20mm f/1.8G ED is an excellent lens to consider adding to your Nikon kit. Images are sharp throughout most of the frame, even at f/1.8, and the lens is sharp from edge-to-edge at f/5.6 and beyond. It's an affordable option, especially when compared with wide-aperture prime lenses like the Nikon AF-S Nikkor 24mm f/1.4G ED ($2,199.95), and zooms that cover the range like the AF-S Nikkor 16-35mm f/4G ED VR ($1,259.95). Video shooters may want to consider the 16-35mm, as its optical stabilization will help to smooth handheld shots, but at f/4 it captures only a quarter of the light as this 20mm f/1.8.

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