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Lens review

Sigma A 12-24 mm f/4 DG HSM

23 October 2016
Szymon Starczewski

7. Coma, astigmatism and bokeh

The Sigma A 12–24 mm f/4 DG HSM corrects the coma quite well. We didn’t observe any problems in the corners of the APS-C/DX sensor; in the corners of full frame you could notice slight deformation of the diode but it was nothing to be worried about. Such results are similar to those from the Canon 11-24 mm and noticeably better than those of the darker predecessor of the Sigma.

Center, 12 mm, f/4.0 Corner APS-C, 12 mm, f/4.0 Corner FF, 12 mm, f/4.0
Sigma A 12-24 mm f/4 DG HSM - Coma, astigmatism and bokeh Sigma A 12-24 mm f/4 DG HSM - Coma, astigmatism and bokeh Sigma A 12-24 mm f/4 DG HSM - Coma, astigmatism and bokeh
Center, 18 mm, f/4.0 Corner APS-C, 18 mm, f/4.0 Corner FF, 18 mm, f/4.0
Sigma A 12-24 mm f/4 DG HSM - Coma, astigmatism and bokeh Sigma A 12-24 mm f/4 DG HSM - Coma, astigmatism and bokeh Sigma A 12-24 mm f/4 DG HSM - Coma, astigmatism and bokeh
Center, 24 mm, f/4.0 Corner APS-C, 24 mm, f/4.0 Corner FF, 24 mm, f/4.0
Sigma A 12-24 mm f/4 DG HSM - Coma, astigmatism and bokeh Sigma A 12-24 mm f/4 DG HSM - Coma, astigmatism and bokeh Sigma A 12-24 mm f/4 DG HSM - Coma, astigmatism and bokeh


When it comes to the astigmatism understood as an average difference between horizontal and vertical MTF50 function values, it amounted to 3.2%. The results below 5% we consider to be low so it seems the Sigma 12-24 mm corrects that off-axis aberration very well; anyway its result is a tad better than the result of the more expensive Canon 11-24 mm.

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With such a focal range and aperture values it is very difficult to get big out-of-focus areas in photos so appraising the lens in this category is a bit art for art’s sake. Still it’s worth noticing that defocused circles of light look sensible; their only flaw is a lighter rim. What’s important, there are no traces of distinct mechanical vignetting.

Center, 24 mm, f/4.0 Corner APS-C, 24 mm, f/4.0 Corner FF, 24 mm, f/4.0
Sigma A 12-24 mm f/4 DG HSM - Coma, astigmatism and bokeh Sigma A 12-24 mm f/4 DG HSM - Coma, astigmatism and bokeh Sigma A 12-24 mm f/4 DG HSM - Coma, astigmatism and bokeh
Center, 24 mm, f/5.6 Corner APS-C, 24 mm, f/5.6 Corner FF, 24 mm, f/5.6
Sigma A 12-24 mm f/4 DG HSM - Coma, astigmatism and bokeh Sigma A 12-24 mm f/4 DG HSM - Coma, astigmatism and bokeh Sigma A 12-24 mm f/4 DG HSM - Coma, astigmatism and bokeh
Center, 24 mm, f/8.0 Corner APS-C, 24 mm, f/8.0 Corner FF, 24 mm, f/8.0
Sigma A 12-24 mm f/4 DG HSM - Coma, astigmatism and bokeh Sigma A 12-24 mm f/4 DG HSM - Coma, astigmatism and bokeh Sigma A 12-24 mm f/4 DG HSM - Coma, astigmatism and bokeh