Tokina AT-X PRO SD 14-20 mm f/2 (IF) DX review - Chromatic and spherical aberration

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

30 March 2016

Arkadiusz Olech

5. Chromatic and spherical aberration

Chromatic aberration

Wide angle Tokinas usually experience a lot of problems when it comes to the correction of chromatic aberration so we were really curious how the 14-20 mm model would perform here. Let’s start with the longitudinal chromatic aberration which assessment we based on photos presented below.

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

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You can notice at once there are no problems whatsoever. Even at the maximum relative aperture the colouring of out-of-focus images remains negligible and it certainly won’t bother you.

Now let’s check the lateral chromatic aberration correction – the graph below presents its values depending on aperture used at particular focal lengths.

For most of combinations of apertures and focal lengths that aberration keeps a steady level of 0.10–0.12% which can be called medium. The biggest differences are at the maximum relative aperture. At the longest focal length the aberration reaches only a low level but at the widest angle it is just under 0.14% so on the borderline between medium and high level. It is important, though, that it never increases to high values; in the case of parameters so difficult to correct you might call it a success.

Canon 50D, 14 mm, f/2.0	Canon 50D, 20 mm, f/2.0

Spherical aberration

In the case of the first photo from this chapter you see that the depth of field shifts very slightly toward the photographer when you pass from f/2.0 to f/2.8. It might be a symptom of the presence of spherical aberration. On the other side its influence cannot be noticed in circles we got in front of and behind the focal point so perhaps that aberration’s level is not especially high.