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Lens review

Sigma 10-20 mm f/3.5 EX DC HSM

25 September 2009
Szymon Starczewski

10. Autofocus

A lens of 10-20 mm focal lengths gives pictures of such a large depth of field that we can often do without the autofocus. For instance, at 10 mm even at the maximum aperture, setting the distance scale at 1.5 meters we get an image sharp from 0.8 meters to infinity.

However, Sigma decided to equip their lens in a silent HSM motor. It does, in fact, work noiselessly and very fast, as going through all the scale takes it less than 0.5 second, no matter the direction.

The combination of a good HSM mechanism and short focal lengths giving a large depth of field resulted in no problems with the autofocus at all. The amount of mistakes in studio conditions reached 1%, which is a slight value. There was no tendency of front- or back-focusing. What’s interesting, Sigma mounted on Nikon D200 performed better than Nikkor 10-24, which with the same camera body showed large front-focus.

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Sigma 10-20 mm f/3.5 EX DC HSM - Autofocus