Sigma A 105 mm f/2.8 DG DN Macro
7. Coma, astigmatism and bokeh
| Center, f/2.8 | Corner APS-C, f/2.8 | Corner FF, f/2.8 |
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| Center, f/4.0 | Corner APS-C, f/4.0 | Corner FF, f/4.0 |
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Astigmatism, understood as an average difference between horizontal and vertical MTF50 function values, amounted to 2.9% and we consider it to be a very low level. As you see, also in this category the lens's performance is beyond reproach.
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Out-of-focus images, generated by the tested Sigma, are also very nice. Light spread in the circles is very even and a brighter rim, appearing on stopping down, is the only feature that might turn your attention. Mechanical vignetting is a different matter, though. It remains visible even on stopping down the aperture by 2 EV; still we are going to tackle that topic in the next chapter.
| Center, f/2.8 | Corner APS-C, f/2.8 | Corner FF, f/2.8 |
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| Center, f/4.0 | Corner APS-C, f/4.0 | Corner FF, f/4.0 |
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Center, f/5.6 | Corner APS-C, f/5.6 | Corner FF, f/5.6 |
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