Sigma A 50 mm f/1.2 DG DN review - Autofocus

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Sigma A 50 mm f/1.2 DG DN

29 August 2024

Maciej Latałło

10. Autofocus

Autofocus

According to the producers the Sigma A 50 mm f/1.2 DG DN is the second Sigma lens so far, after the S 70-200 mm f/2.8 DG DN OS, that features the linear HLA motor (High-response Linear Actuator). The focus is supposed to be set very quickly and be exceptionally quiet.

Our test experience confirms that much. The tested Sigma joined with the Sony A7R IIIa is noiseless and really fast. Running through the whole distance range and confirming the focus in the majority of cases takes less than 0.3 of a second, an excellent result. Here the Sigma should be only praised.

We also didn't have any serious problems with the accuracy of the mechanism. Both in our studio and outside in the majority of cases the focus was set where it should.

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Still when we took photos from very short distances we noticed a very slight tendency to front focus – the photo below shows it very clearly.

A7R IIIa, f/1.2

Focus breathing

Focus breathing tests show refraiming images as you oversharp them. We conduct the test by manually passing from the minimum focusing distance to infinity with the aperture stopped down; then we check how the field of view of the lens changed as a result.

A frame change ranging from 0 to 5% we consider to be low. Between 5 and 10% you can speak about medium levels. Usually such values constitute also the maximum efficiency level of any breathing compensation algorithms, present in some bodies. Between 10 and 15% focus breathing is high, above 15% its level can be called very high.

The test video of the Sigma lens is presented below:

On the basis of the recording above, comparing freeze-frames before and after oversharpening, we can estimate that the breathing of the tested lens amounts to about 6% which is a lower border of medium levels.

The breathing result is not perfect but still we have to praise the Sigma for a more serious approach toward breathing correction in their lenses. The not much older 50 mm f/1.4 DG DN Art model had a huge slip-u in this category, with focus breathing of 19%. We hope Sigma will continue this trend and correct this aberration in all future launches even better.