Nikon Nikkor AF-S 20 mm f/1.8G ED
5. Chromatic and spherical aberration
Fast Nikkors rarely correct the longitudinal chromatic aberration well. The crops below show the results of the Nikkor 1.8/20.
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It should be clearly stated: those results look sensible. At the maximum relative aperture you see slight cast of images registered behind the focal point but that effect is not distinct. What’s important, it decreases significantly on stopping down the aperture.
Let’s check the lateral chromatic aberration performance now – the graph below shows the connection between it and the aperture values.
Here the lens should definitely be praised. Correcting that aberration while you feature such a wide angle of view and such a fast aperture is certainly difficult but the Nikkor managed it splendidly. No matter what detector and what aperture you apply, the lateral aberration keeps near a very low level of 0.06-0.07%. A round of applause!
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Spherical aberration
The lens didn’t show any „focus shift” effect. What’s more, the defocused circles of light we got in front of and behind the focus didn’t differ distinctly. Both these facts prove that the spherical aberration is corrected properly by the tested lens.
