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Lens review

Tokina AT-X PRO DX 11-20 mm f/2.8

8 September 2015
Arkadiusz Olech

5. Chromatic and spherical aberration

Chromatic aberration

Ultra wide angle lenses usually don’t have any problems with the correction of the longitudinal chromatic aberration because of their mediocre fastness. The tested Tokina, though, featuring f/2.8 relative aperture, had it more difficult in this category. Still it managed to perform very well here because its defocused images are characterized by just traces of colouring.



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Tokina AT-X PRO DX 11-20 mm f/2.8 - Chromatic and spherical aberration


When it comes to the lateral chromatic aberration it has to be said the wide angle Tokinas often failed to correct it well. What about this one? Let’s glance at a graph below.

Tokina AT-X PRO DX 11-20 mm f/2.8 - Chromatic and spherical aberration


There are certainly no reasons to be happy – at the most difficult combination of the 11 mm focal length and the f/2.8 aperture the aberration reaches a high level of 0.18%. What’s more, it never decreases below 0.14% at any combination of aperture and focal length, being perfectly visible. Still when you compare that to the results of the 11-16 mm f/2.8 model where you had to deal with a level of 0.22-0.27% you have to notice a very distinct improvement which should be appreciated. However it is not enough to defeat the direct rival of the Tokina, the Sigma 10–20 mm f/3.5 EX DC HSM.

Canon 50D, 11 mm, f/2.8 Canon 50D, 20 mm, f/5.6
Tokina AT-X PRO DX 11-20 mm f/2.8 - Chromatic and spherical aberration Tokina AT-X PRO DX 11-20 mm f/2.8 - Chromatic and spherical aberration



Spherical aberration

We didn’t observe any focus shift effect but it could be masked by the significant depth of field stemming from the parameters of the tested lens. Still the spherical aberration of the lens cannot be corrected in a perfect way because the circles of light we got behind the focus have a very distinct rim with a dark centre and there is no such an effect in the circles in front of the focus.

Canon 50D, 20 mm, f/2.8, in front of Canon 50D, 20 mm, f/4.0, behind
Tokina AT-X PRO DX 11-20 mm f/2.8 - Chromatic and spherical aberration Tokina AT-X PRO DX 11-20 mm f/2.8 - Chromatic and spherical aberration