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Lens review

2010-06-09
 

Tokina AT-X 165 PRO DX AF 16-50 mm f/2.8

7. Coma and astigmatism

Looking at the pictures below you can immediately say that the coma contributes a lot to worsening of the image quality at the frame edge at all focal lengths. However, both the Sigma and the Tamron experienced similar problems as well; only the more expensive Canon 17-55 mm fared better.

Tokina AT-X 165 PRO DX AF 16-50 mm f/2.8 - Coma and astigmatism

Fortunately, the astigmatism is not one the Tokina’s problems; understood as the average difference between vertical and horizontal MTF50 function values, it amounted to just 5%.

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Canon 20D

In the case of the 20D the coma looks very much alike. Average astigmatism reaches 6.7% - it is a result not much higher than on the Nikon. With the lengthening of the focal length you can notice a growth trend, though, and it makes this aberration increase to almost 12% at 50 mm, contributing significantly to weak results at that focal length.

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