Sigma A 50-100 mm f/1.8 DC HSM review - Coma, astigmatism and bokeh

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Sigma A 50-100 mm f/1.8 DC HSM

26 April 2016

Arkadiusz Olech

7. Coma, astigmatism and bokeh

The coma is often bothersome in the case of fast lenses – it’s enough to glance at our tests of 1.8/50 class instruments to find out what problems it might cause. That’s why the Sigma A 50-100 mm f/1.8 DC HSM gained our recognition in this category: look at photos below and it is clear the lens manages to correct the coma in a splendid way. A round of applause!

50D, 50 mm, f/1.8, center	50D, 50 mm, f/1.8, corner

50D, 75 mm, f/1.8, center	50D, 75 mm, f/1.8, corner

50D, 100 mm, f/1.8, center	50D, 100 mm, f/1.8, corner

The astigmatism, understood as an average difference between horizontal and vertical MTF50 function values, amounted to just 2.4% which we consider very low. The fact that it didn’t depend on the focal length is also worth mentioning.

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When it comes to the appearance of blurry areas the Sigma presents a very good level for a zoom lens. The light spread in light circles is very even, without any distinct local extremes or onion rings. On stopping down the aperture there is a rim on the edge of the circle but still its intensity is not especially high.

50D, 100 mm, f/1.8, center	50D, 100 mm, f/1.8, corner

50D, 100 mm, f/2.5, center	50D, 100 mm, f/2.5, corner

50D, 100 mm, f/3.5, center	50D, 100 mm, f/3.5, corner