Sigma 10-20 mm f/4-5.6 EX DC HSM review - Distortion

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Sigma 10-20 mm f/4-5.6 EX DC HSM

13 October 2010

Arkadiusz Olech

6. Distortion

Here we deal with the situation identical to that of the Canon 10-22 mm because in both lenses the same mapping was used, which strives to render straight lines as straight. Taking photos of test charts featuring the grid of straight lines, which plane is parallel to the plane of the detector, we see results different lenses with the focal lengths starting from 17-18 mm would envy. At 10 mm we have a slight barrel distortion which value was determined as –0.88%. At 15 mm it swiftly turns into “pincushion” at the level of 1.3%; at 20 mm it decreases to 0.9%. None of these values is bothersome as you can see in the photos below.

Sigma 10-20 mm f/4-5.6 EX DC HSM - Distortion

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Saying that ultra wideangle devices of the Sigma’s 10-20 mm class don’t show any geometric deformations is a serious abuse. All deformations increase rapidly the very moment when the photographed plane is situated at even small angle to the sensor’s plane. The photos below show it very clearly. We put the camera in front of a door and we took three pictures, keeping all the time the distance between the camera and the wall was the same. In the first photo the camera was positioned perfectly opposite the door, in the second picture we moved it a bit to the right, keeping the planes of the sensor and of the door parallel, and in the third shot we put the camera at a small angle towards the door. The effect was instantaneous. The door’s surface became seriously deformed.