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Lens review

Sigma A 12-24 mm f/4 DG HSM

23 October 2016
Szymon Starczewski

10. Autofocus

The tested lens was equipped with an HSM ultrasonic autofocus motor so its performance is practically noiseless. You should also praise the speed. Running through the whole distance range and finding the focus takes about 0.6˗0.8 of a second which is a good result. It’s worth mentioning that the Sigma faced a more difficult task than its predecessor and the Canon 11–24 mm because its minimum focusing distance amounts to just 20 cm so the summary range it has to serve is bigger.

With such parameters of the lens the depth of field is so significant, though, that it can forgive small autofocus mistakes. As a result in studio conditions the lens didn’t miss one single time. Also while working with the lens outside we didn’t have any reservations concerning its autofocus performance.

When it comes to front or back focus tendency we didn’t notice any huge problems while the lens was attached to any of the bodies used by us in the test. In photos below the target is situated firmly within the depth of field even though it might seem shifted towards the camera. Such an effect is not necessarily connected to the autofocus; it might be a result of e.g. field curvature.

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Canon 50D, 24 mm, f/4.0
Sigma A 12-24 mm f/4 DG HSM - Autofocus
Canon 5D III, 24 mm, f/4.0
Sigma A 12-24 mm f/4 DG HSM - Autofocus