Sigma A 50 mm f/1.2 DG DN review - Coma, astigmatism and bokeh

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Sigma A 50 mm f/1.2 DG DN

29 August 2024

Maciej Latałło

7. Coma, astigmatism and bokeh

The Sigma A 50 mm f/1.2 DG DN doesn't have any serious coma-related problems. That aberration remains practically invisible in the corners of the APS-C/DX and it makes itself felt in the very corner of full frame. Still, even there it is situated on the borderline between low and medium levels. What's more, this performance seems to be a tad better than the performance of the Sony 1.2/50 GM.

Center, f/1.2	Corner APS-C, f/1.2	Corner FF, f/1.2

Center, f/1.8	Corner APS-C, f/1.8	Corner FF, f/1.8

Astigmatism, understood as an average difference between horizontal and vertical MTF50 function values, amounted to just 3.4%. It is an excellent result, once again better than in case of the more expensive rival.

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The appearance of out-of-focus images leaves something to be desired. From a lens with such a fast aperture you expect a perfect shape of circles of light and here the high number of aspherical elements makes itself felt in a form of distinct onion-ring bokeh. The precision of Sigma's aspherical elements is apparently inferior to similar elements in the construction of the rival Sony which didn't show such a distinct onion rings in our test.

Limiting dimensions of the Sigma also provided an effect of mechanical vignetting – it makes itself felt even on stopping down the lens by 2 EV. Once again the Sigma is defeated in this area by the Sony.

Center, f/1.2	Corner APS-C, f/1.2	Corner FF, f/1.2

Center, f/1.8	Corner APS-C, f/1.8	Corner FF, f/1.8

Center, f/2.5	Corner APS-C, f/2.5	Corner FF, f/2.5