Tokina AT-X PRO SD 14-20 mm f/2 (IF) DX review - Coma, astigmatism and bokeh

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Tokina AT-X PRO SD 14-20 mm f/2 (IF) DX

30 March 2016

Arkadiusz Olech

7. Coma, astigmatism and bokeh

The Tokina AT-X PRO SD 14–20 mm f/2 (IF) DX corrects the coma quite well as you can notice by glancing at photos below. In the frame corners, no matter what focal length you employ, even at the maximum relative aperture the image of the diode is only slightly disfigured. In this category the constructors of the lens deserve our praise because the combination of f/2.0 aperture and an angle of view of over 90 degrees can hardly be called easy to correct that aberration.

50D, 10 mm, f/2.0, center	50D, 10 mm, f/2.0, corner

50D, 17 mm, f/2.0, center	50D, 17 mm, f/2.0, corner

50D, 20 mm, f/2.0, center	50D, 20 mm, f/2.0, corner

The astigmatism, understood as an average difference between horizontal and vertical MTF50 function values, amounted to 3.2% which we consider a very low level. It’s worth mentioning that at 20 mm it was slightly higher than for the rest of focal lengths.

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When it comes to the appearance of out-of-focus images it would be difficult to have any reservations here. The light spread is even and the aperture blades make the circles very pleasantly round. You can notice a lighter rim but it is acceptable in the case of a zoom lens. It is obvious the lens has no big problems with the mechanical vignetting – even in the frame corner by f/2.0 the circle we got wasn’t especially truncated.

50D, 20 mm, f/2.0, center	50D, 20 mm, f/2.0, corner

50D, 20 mm, f/2.8, center	50D, 20 mm, f/2.8, corner

50D, 20 mm, f/4.0, center	50D, 20 mm, f/4.0, corner