Sigma C 15 mm f/1.4 DC review

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Sigma C 15 mm f/1.4 DC

21 May 2026

Maciej Latałło

7. Coma, astigmatism and bokeh

Photos below show clearly that coma is not corrected in a perfect way and it negatively influences image quality on the edge of the frame. Of course we should emphasize the fact that you don't deal with a high level of this problem. Images of a diode are influenced by coma itself, as they turn into a slight comma. High-degree aberrations, responsible for characteristic 'wings' are corrected very well indeed.

The current model fares here slightly better than its predecessor, which had to tackle not only high coma level but also aberrations of higher degrees – in its case these 'wings' were distinctly visible and they didn't disappear completely even after stopping down the aperture by 1 EV. When it comes to a comparison between the tested lens and the Sony the new Sigma is weaker because the dimensions of the Sony's 'comma' are a tad smaller.

A7R V, APS-C f/1.4, centre	A7R V, APS-C, f/1.4, corner

A7R V, APS-C, f/2.0, centre	A7R V, APS-C, f/2.0, corner

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To make our test more comprehensive, we decided to show crops taken from photos of night sky taken from the right-hand upper corner. This time we show images taken by f/1.4, f/2.0, and f/2.8. As you see this part of the test confirms our earlier conclusions.

Corner, f/1.4	Corner, f/2.0	Corner, f/2.8

Astigmatism, understood as an average difference between horizontal and vertical MTF50 values, amounted to 5.9%. It's a level on the borderline between very low and low values, which shouldn't worry you. Once again, the Sigma deserves to be praised for its performance. At the same time, you can add that this result is exactly the same as the result of the Sony and distinctly lower than the result of the predecessor.

Defocused circles of light look really good for a wide angle lens. Despite using as many as three aspherical elements, the onion-ring bokeh is not especially felt. The circles also don't show any pronounced local extreme points; the only thing that can be noticed is a brighter rim whose intensity increases slightly on stopping down.

Small dimensions of the lens make themselves felt in case of mechanical vignetting and this effect is perfectly visible by f/1.4 and f/2.0. What's more, even by f/2.8 the vignetting remains slightly accented.

A7R V, APS-C, f/1.4, centre	A7R V, APS-C, f/1.4, corner

A7R V, APS-C, f/2.0, centre	A7R V, APS-C, f/2.0, corner

A7R V, APS-C, f/2.8, centre	A7R V, APS-C, f/2.8, corner