Tamron 20-40 mm f/2.8 Di III VXD
5. Chromatic and spherical aberration
Chromatic aberration
In the optical system of the tested Tamron you get a lot of elements made of low dispersion glass and the results of our chromatic aberration tests show that it was a good idea. The longitudinal variant of this aberration is on a very low level – only at the maximum relative aperture and in out-of-focus areas situated in greater distances you can notice any colouring of images. Such an effect will be practically imperceptible in real life photos. |
Two graphs, shown below, represent lateral chromatic aberration performance depending on the focal length and aperture; the first one concerns the edge of the APS-C sensor, the second one – the edge of full frame.
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As you see, the differences between particular focal lengths are slight and most of results range from 0.03% to 0.05%. These are values on the borderline between very low and low level so, taking into account offered angles of view and aperture fastness of the tested Tamron, we think it deserves to be praised in this category.
| A7R III, RAW, 20 mm, f/2.8 | A7R III, RAW, 40 mm, f/11.0 |
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Spherical aberration
First photos of this chapter don't show any noticeable focus shift effect. When it comes to defocused circles of light the only difference between them is a brighter rim. All this proves that the problems with spherical aberration are minor and the tested lens deals with its correction quite well.
| A7R III, 40 mm, f/2.8, before | A7R III, 40 mm, f/2.8, after |
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