Sony FE 85 mm f/1.4 GM
5. Chromatic and spherical aberration
Chromatic aberration
While the resolution performance of the Sony FE 1.4/85 GM fits more modern portrait lenses, the longitudinal chromatic aberration correction is closer to that of older constructions. The aberration is distinct at the maximum relative aperture and remains visible even on stopping down the lens to f/2.0. It is a very surprising result, taking into account the fact the lens’s optical construction features as many as three low dispersion elements.
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Fortunately the lens corrects the lateral chromatic aberration in a far better way and the graph shown below is the proof.
Apart from a slight local maximum point by f/2.0 the results amount to a low level of 0.04% everywhere. The lateral chromatic aberration shouldn’t be visible in real life photos at all.
| A7R II, RAW, f/2.0 | A7R II, RAW, f/11.0 |
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Spherical aberration
The Sony FE 1.4/85 GM has some spherical aberration problems which contribute to the worsening of images near the maximum relative aperture. Firstly, they can be noticed as a slight focus shift effect. In the first photo of this chapter you see that on passing from f/1.4 to f/2.0 the depth of field moves toward the longer end of the focal spectrum. Secondly, the spherical aberration makes itself felt also influencing the shape of circles of light. One of them features soft edges and the second one – a distinct, lighter rim. These are classic signs of the presence of that aberration.
| A7R II, f/1.4, in front of | A7R II, f/1.4, behind |
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