Canon EF 20mm f/2.8 USM review

The Canon EF 20mm f/2.8 USM lens delivers an ultra-wide field of view on full-frame cameras, and is quite sharp once you stop down to f/4.
Photo of Canon EF 20mm f/2.8 USM

The Canon EF 20mm f/2.8 USM ($539.99 direct) is a fairly compact wide-angle lens for Canon D-SLR cameras. When used on a full-frame body, the lens can capture stunning landscapes, and its distortion characteristics are controlled enough for use for architecture. Mounting it to an APS-C camera like the EOS Rebel T4i gives the lens a narrower 32mm field of view, which is still considered to be a moderate wide angle.

When you consider its field of view, the lens is pretty compact. It measures just 2.8 by 3.1 inches (HD) and adds 14.3 ounces of weight to your gear bag. It can focus as close as 0.8-foot, which allows you to get some interesting shots with a shallow depth of field, but when shooting wider scenes the lens will keep everything in focus, as racking it to infinity will put every object more than three feet from the lens in sharp focus. The front element is slightly curved, but you can still use a screw-in filter with the lens—you’ll just have to invest in one with a rather large 72mm diameter. As is the case with almost every prime lens, the front element doesn’t rotate when focusing, so using a polarizer is possible. The lens hood is not included, although adding one is probably a good idea as wide-angle lenses are often prone to flare and a hood will help to compensate for that.

Imatest shows that the lens is a little soft at f/2.8, but sharpens nicely from f/4 onwards. At its widest aperture it records 1,689 lines per picture height, just a bit shy of the 1,800 lines that are required for an image to be considered sharp. It hits 1,963 lines at f/4, increases to 2,245 lines at f/5.6, and peaks at 2,374 lines at f/8. The lens shows only 0.2 percent pincushion distortion when paired with the full-frame Canon EOS 6D, an impressive result. There is some evidence of color fringing in high-contrast scenes, especially tree branches against a bright sky. This can be corrected in Lightroom with a few adjustments. We didn’t notice fringing when we shot with Canon’s EF 17-40mm f/4L USM zoom lens on the EOS 5D Mark III. That lens is also quite sharp and has zoom capability, but is a bit more expensive and shows much more distortion at wide angles.

If you’re in the market for a wide prime lens for your Canon camera, the EF 20mm f/2.8 USM is a solid choice. It has a moderately fast aperture, and sharpens quickly as you narrow its iris. The price is quite reasonable, and it can be used with both full-frame and APS-C cameras. On the former it captures a truly wide field of view, and on the latter serves as a very useful moderate wide-angle optic.

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Verdict
The Canon EF 20mm f/2.8 USM lens delivers an ultra-wide field of view on full-frame cameras, and is quite sharp once you stop down to f/4.
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