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Lens review

Sigma A 24-70 mm f/2.8 DG OS HSM

28 July 2017
Maciej Lata³³o

10. Autofocus

The Sigma A 24–70 mm f/2.8 DG OS HSM is equipped with an ultrasonic autofocus motor so its performance is noiseless. We don't have any reservations concerning the speed either. For the beginning and the middle of the focal lengths range running through the whole distance range and setting the focus takes less than 0.3 of a second which is a fantastic result. At 70 mm the whole process takes a bit longer but still you deal with a very good performance on a level of 0.4 of a second.

The accuracy performance we assess positively, both in the studio and outdoor. For the most difficult combination of the 70 mm focal length and f/2.8 aperture, with the lens positioned before a testing chart, you might count on 88% of hits accurate within just 5% of difference from the best result. A bit worse hits but still completely acceptable (from 5 to 10% of difference from the best result) constituted 7% of all shots.There were 5% of shots considered by us to be totally missfocused (different by more than 20% from the sharpest photo). The results at the shorter end of the focal spectrum were even better due to the increase of the depth of field.

As you can notice in photos below the lens didn't need any microcalibration on both bodies we used in our test.

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Canon 50D, 45 mm, f/2.8
Sigma A 24-70 mm f/2.8 DG OS HSM - Autofocus
Canon 50D, 70 mm, f/2.8
Sigma A 24-70 mm f/2.8 DG OS HSM - Autofocus
Canon 5D Mk III, 45 mm, f/2.8
Sigma A 24-70 mm f/2.8 DG OS HSM - Autofocus
Canon 5D Mk III, 70 mm, f/2.8
Sigma A 24-70 mm f/2.8 DG OS HSM - Autofocus