LensTip.com

Lens review

Sigma A 24-70 mm f/2.8 DG DN

22 January 2020
Arkadiusz Olech

7. Coma, astigmatism and bokeh

Across the whole area covered by APS-C detector and also in the corner of full frame coma is corrected very well but only in the middle of the focal lengths range. On both ends of the range coma remains visible and it can contribute to worsening of image quality. Still the situation is notably better than in the case of the Tamron 28-75 mm f/2.8 Di III RXD.

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 DN - Coma, astigmatism and bokeh Sigma A 24-70 mm f/2.8 DG DN - Coma, astigmatism and bokeh Sigma A 24-70 mm f/2.8 DG DN - 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 DN - Coma, astigmatism and bokeh Sigma A 24-70 mm f/2.8 DG DN - Coma, astigmatism and bokeh Sigma A 24-70 mm f/2.8 DG DN - 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 DN - Coma, astigmatism and bokeh Sigma A 24-70 mm f/2.8 DG DN - Coma, astigmatism and bokeh Sigma A 24-70 mm f/2.8 DG DN - Coma, astigmatism and bokeh


Astigmatism, understood an an average difference between vertical and horizontal MTF50 function values, amounted to 3.9% and it is a low level. The reflex camera Sigma A 24-70 mm f/2.8 DG HSM fared weaker in this category as in its case we got a result of 12.7%. The tested Sigma also performs better than the rival Tamron in this category.


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Defocused cricles of light aren't perfect – you can have reservations concerning slight onion-ring bokeh visible inside the circles which, most probably, stems from using as many as three aspherical elements. Also a lighter rim makes itself felt and its intensity increases with stopping down the aperture. It would be difficult to miss the influence of mechanical vignetting which, by f/2.8, cuts out almost half of the circle. In the next chapter such a performance will be keenly felt for sure.

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 DN - Coma, astigmatism and bokeh Sigma A 24-70 mm f/2.8 DG DN - Coma, astigmatism and bokeh Sigma A 24-70 mm f/2.8 DG DN - 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 DN - Coma, astigmatism and bokeh Sigma A 24-70 mm f/2.8 DG DN - Coma, astigmatism and bokeh Sigma A 24-70 mm f/2.8 DG DN - 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 DN - Coma, astigmatism and bokeh Sigma A 24-70 mm f/2.8 DG DN - Coma, astigmatism and bokeh Sigma A 24-70 mm f/2.8 DG DN - Coma, astigmatism and bokeh