Sigma A 85 mm f/1.4 DG HSM review - Coma, astigmatism and bokeh

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Sigma A 85 mm f/1.4 DG HSM

16 November 2016

Arkadiusz Olech

7. Coma, astigmatism and bokeh

The Sigma A 85 mm f/1.4 DG HSM doesn’t have any coma-related problems – the shape of the diode is deformed just slightly even in the corners of full frame at the maximum relative aperture. Similarly performed the Milvus 1.4/85 but the Otus 1.4/85 was a tad weaker; on the other hand such models as the Canon 1.2/85, Sigma EX 1.4/85 or the Nikkor 1.4/85G had noticeably worse results.

Center, f/1.4	Corner APS-C, f/1.4	Corner FF, f/1.4

Center, f/2.0	Corner APS-C, f/2.0	Corner FF, f/2.0

Astigmatism, understood as an average difference between vertical and horizontal MTF50 function values amounted to just 1.7%. It is a negligible level and, officially, the lowest result of all 85 mm devices we present in this test.

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When it comes to the appearance of out-of-focus images we don’t have any reservations. The light spread in circles is very even, without any distinct rims or local extremes. Still the significant truncation of circles in the frame corners is a bit worrisome – it is a trait of mechanical vignetting and we didn’t expect to see it in a test of a lens so big.

Center, f/1.4	Corner APS-C, f/1.4	Corner FF, f/1.4

Center, f/2.0	Corner APS-C, f/2.0	Corner FF, f/2.0

Center, f/2.8	Corner APS-C, f/2.8	Corner FF, f/2.8