Viltrox PFU RBMH 85 mm f/1.8 STM
5. Chromatic and spherical aberration
Chromatic aberration
Despite low dispersion glass, used in the optical construction of the lens, longitudinal chromatic aberration is not corrected perfectly well. Near the maximum relative aperture it's easy to notice colouring of out-of-focus images. The effect is perhaps not especially pronounced but certainly can be bothersome in some situations. In this category the Viltrox lags behind the Sony for sure. |
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Now let's see how the tested lens corrects lateral chromatic aberration – below we present appropriate graph with results depending on the aperture and the used detector.
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Fortunately, there are no problems here. The aberration in most of cases is low, near the maximum relative aperture even very low. Overall the graph is similar to the performance of the Sony 1.8/85 FE but that lens's results could approach even 0.09%, brushing against medium levels. It seems in this category the Viltrox prevails.
| A7R II, RAW, f/1.8 | A7R II, RAW, f/11.0 |
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Spherical aberration
First photos of this chapter don't show even the slightest symptoms of „focus shift” effect so spherical aberration cannot be high or very high. Defocused circles of light also are nothing to worry about because differences between them are small, less pronounced than differences between circles of light generated by the Sony. We have every reason to think that, out of these two lenses, it's the Viltrox that corrects spherical aberration a bit better. It might explain why by f/1.8 and f/2.0 it provides images of better resolution than the Sony.
| A7R II, f/1.8, in front of | A7R II, f/1.8, behind |
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