LensTip.com

Lens review

Sigma 17-50 mm f/2.8 EX DC OS HSM

30 July 2010
Arkadiusz Olech

7. Coma and astigmatism



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Coma shows a distinct decreasing tendency with the increase of the focal length. At 17 mm it is very noticeable, at 30 mm – medium and at 50 mm a bit lower than medium. This performance can partially explain why exactly at 50 mm focal length you reach the best results when it comes to the sharpness of the image at the frame edge.

Sigma 17-50 mm f/2.8 EX DC OS HSM - Coma and astigmatism

There will be no problem with astigmatism because the Sigma 17-50 mm f/2.8 corrects it perfectly. The average difference between vertical and horizontal MTF50 function values amounted to just 2.4%.