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