Tokina AT-X PRO DX 11-20 mm f/2.8 review - Distortion

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Tokina AT-X PRO DX 11-20 mm f/2.8

8 September 2015

Arkadiusz Olech

6. Distortion

Lenses in the style of the Tokina 11–16 mm or the 11–20 mm tested here, use rectilinear projection which doesn’t curve straight lines that much, providing a narrower field of view at a given focal length than the projection used in a ‘fisheye’ lens. Still it causes strong deformations in the corners of the frame. It’s good to go back to your geography class and remind here the world map as the gnomonic projection, where the meridians and parallels are shown as straight lines. Although the surface deformation of countries and continents around the equator and the tropics was not very distinct, it was always weird to see the huge size of Greenland next to the North Pole, which looked completely different on your ordinary globe.

Most of ultra wide angle lenses tested on small sensors have barrel distortion of around −2% at the widest angle and then it usually decreases below −1% at the longer end of the focal range. The Tokina 11-16 mm II didn’t impress us in this category because at 11 mm it had a noticeable level of barrel distortion amounting to −2.95%. We were very curious how the 11-20 mm model would fare here; it is known that the increase of the focal range makes it more difficult to correct distortion.

The result at the widest angle worsened a bit and it amounts to −3.15% now. Still it is a small and completely acceptable price to pay for the increase of the focal length. The rivals, though, are better in this category.

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The problems disappear when you pass to the higher focal lengths. At 16 mm you get a distortion level of −0.73%, and at 20 mm that of −0.21%. Those values shouldn’t bother you at all.