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Lens review

Sigma A 85 mm f/1.4 DG HSM

16 November 2016
Szymon Starczewski

10. Autofocus

The autofocus mechanism of the Sigma joined with both bodies used in our test (the 50D and the 5D Mk III) was noiseless and decently fast. Running through the whole distance scale, no matter from what end, took about 0.5–0.6 of a second. It is a sensible result which doesn’t change noticeably in worse lighting conditions.

When it comes to poor lighting conditions the Sigma attached to the 5D Mark III seemed to perform actually better than its rivals. During a studio session with the modelling light switched off it was quite dark; still the Sigma managed to set the focus without any problems every single time. In the same conditions the Nikon D3x with the new Nikkor AF-S 105 mm f/1.4 performed much worse, its AF mechanism often getting lost and trying to find appropriate position several times.

When it comes to the accuracy the Sigma results were very good – in studio conditions the lens hardly ever missed. It also didn’t need any calibration when attached to any of the bodies, and photos below are the proof.

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Canon 50D, f/1.4
Sigma A 85 mm f/1.4 DG HSM - Autofocus
Canon 5D MkIII, f/1.4
Sigma A 85 mm f/1.4 DG HSM - Autofocus


In order to be absolutely sure our results were right we took two additional tests, similar to those we perform while testing cameras. We put the Sigma attached to the EOS 5D Mark III before one of our charts and, by f/2.8 we took 50 photos setting the focus every time anew. There were 59% of shots with perfect sharpness, 39% of photos with errors smaller than 20% of the maximum MTF50 and only 2% of shots which should be considered complete misses.

Then we raised the standards even higher and repeated the experiment by f/1.4. What’s interesting, the results were even better, with 75% of perfectly sharp photos, 23% of acceptable ones and once again just 2% of misses.