LensTip.com

Lens review

Sigma C 65 mm f/2 DG DN

27 February 2021
Maciej Latałło

5. Chromatic and spherical aberration

Chromatic aberration

The optical construction of the Sigma C 2/65 features just one low dispersion ED glass element and, it seems, it's not enough to eliminate longitudinal chromatic aberration completely. Its influence, in a form of slight colouring of out-of-focus images, can be noticed mainly near the maximum relative aperture. Fortunately, it's not a very serious or even moderately serious flaw.

Sigma C 65 mm f/2 DG DN - Chromatic and spherical aberration


What about lateral chromatic aberration? Let's glance at a graph below and find out.

Sigma C 65 mm f/2 DG DN - Chromatic and spherical aberration


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Its highest level is reached near the maximum relative aperture bu even there the results can be placed on a borderline between very low and low level. On stopping down they drop below 0.04% and it means that aberration becomes practically imperceptible.

A7R III, RAW, FF, f/2.0 A7R III, RAW, FF, f/8.0
Sigma C 65 mm f/2 DG DN - Chromatic and spherical aberration Sigma C 65 mm f/2 DG DN - Chromatic and spherical aberration

Spherical aberration

First photos of this chapter don't show any noticeable 'focus shift' effect. When it comes to circles of light reached before and behind the focal point they aren't identical. In fact you can notice a textbook example of spherical aberration that hasn't been corrected properly well - the edge of one circle is soft and the second circle features a brighter rim.

A7R III, f/2.0, before A7R III, f/2.0, after
Sigma C 65 mm f/2 DG DN - Chromatic and spherical aberration Sigma C 65 mm f/2 DG DN - Chromatic and spherical aberration