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Lens review

Sigma A 24-70 mm f/2.8 DG OS HSM

28 July 2017
Maciej Latałło

7. Coma, astigmatism and bokeh

We didn't notice any coma-related problems on the smaller sensor of the Canon 50D. They appear only in the corners of full frame and are the most pronounced at the 24 mm focal length. In the 45-70 mm range that aberration is corrected slightly better but still not perfectly well.

In this category the Sigma fares better than the Tokina and the Tamron VC but it remains weaker than the stabilized Nikkor ant the Canon 24-70 mm f/2.8 II.

Center, 24 mm, f/2.8 Corner APS-C, 24 mm, f/2.8 Corner FF, 24 mm, f/2.8
Sigma A 24-70 mm f/2.8 DG OS HSM - Coma, astigmatism and bokeh Sigma A 24-70 mm f/2.8 DG OS HSM - Coma, astigmatism and bokeh Sigma A 24-70 mm f/2.8 DG OS HSM - Coma, astigmatism and bokeh
Center, 45 mm, f/2.8 Corner APS-C, 45 mm, f/2.8 Corner FF, 45 mm, f/2.8
Sigma A 24-70 mm f/2.8 DG OS HSM - Coma, astigmatism and bokeh Sigma A 24-70 mm f/2.8 DG OS HSM - Coma, astigmatism and bokeh Sigma A 24-70 mm f/2.8 DG OS HSM - Coma, astigmatism and bokeh
Center, 70 mm, f/2.8 Corner APS-C, 70 mm, f/2.8 Corner FF, 70 mm, f/2.8
Sigma A 24-70 mm f/2.8 DG OS HSM - Coma, astigmatism and bokeh Sigma A 24-70 mm f/2.8 DG OS HSM - Coma, astigmatism and bokeh Sigma A 24-70 mm f/2.8 DG OS HSM - Coma, astigmatism and bokeh

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Astigmatism, understood as an average difference between horizontal and vertical MTF50 function values, amounted to 12.7%, a level we consider to be moderate. It's worth adding that the maximum focal length contributes the most as its astigmatism reaches 16.5%. In this category the Sigma is easily defeated by its direct rivals.

Defocused circles of light aren't perfect either. An „onion rings” effect which appears on stopping down the lens and a peak in the centre of the circle are a bit annoying. At 70 mm you can also notice distinct influence of mechanical vignetting.

Center, 45 mm, f/2.8 Corner APS-C, 45 mm, f/2.8 Corner FF, 45 mm, f/2.8
Sigma A 24-70 mm f/2.8 DG OS HSM - Coma, astigmatism and bokeh Sigma A 24-70 mm f/2.8 DG OS HSM - Coma, astigmatism and bokeh Sigma A 24-70 mm f/2.8 DG OS HSM - Coma, astigmatism and bokeh
Center, 45 mm, f/4.0 Corner APS-C, 45 mm, f/4.0 Corner FF, 45 mm, f/4.0
Sigma A 24-70 mm f/2.8 DG OS HSM - Coma, astigmatism and bokeh Sigma A 24-70 mm f/2.8 DG OS HSM - Coma, astigmatism and bokeh Sigma A 24-70 mm f/2.8 DG OS HSM - Coma, astigmatism and bokeh
Center, 45 mm, f/5.6 Corner APS-C, 45 mm, f/5.6 Corner FF, 45 mm, f/5.6
Sigma A 24-70 mm f/2.8 DG OS HSM - Coma, astigmatism and bokeh Sigma A 24-70 mm f/2.8 DG OS HSM - Coma, astigmatism and bokeh Sigma A 24-70 mm f/2.8 DG OS HSM - Coma, astigmatism and bokeh

Center, 70 mm, f/2.8 Corner APS-C, 70 mm, f/2.8 Corner FF, 70 mm, f/2.8
Sigma A 24-70 mm f/2.8 DG OS HSM - Coma, astigmatism and bokeh Sigma A 24-70 mm f/2.8 DG OS HSM - Coma, astigmatism and bokeh Sigma A 24-70 mm f/2.8 DG OS HSM - Coma, astigmatism and bokeh
Center, 70 mm, f/4.0 Corner APS-C, 70 mm, f/4.0 Corner FF, 70 mm, f/4.0
Sigma A 24-70 mm f/2.8 DG OS HSM - Coma, astigmatism and bokeh Sigma A 24-70 mm f/2.8 DG OS HSM - Coma, astigmatism and bokeh Sigma A 24-70 mm f/2.8 DG OS HSM - Coma, astigmatism and bokeh
Center, 70 mm, f/5.6 Corner APS-C, 70 mm, f/5.6 Corner FF, 70 mm, f/5.6
Sigma A 24-70 mm f/2.8 DG OS HSM - Coma, astigmatism and bokeh Sigma A 24-70 mm f/2.8 DG OS HSM - Coma, astigmatism and bokeh Sigma A 24-70 mm f/2.8 DG OS HSM - Coma, astigmatism and bokeh