Sigma C 35 mm f/2 DG DN review - Vignetting

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Sigma C 35 mm f/2 DG DN

8 January 2021

Maciej Latałło

8. Vignetting

First let's check how the lens fares in this category on the smaller APS-C sensor – appropriate thumbnails you can find below.

A7R II, APS-C, f/2.0	A7R II, APS-C, f/2.8

In this case there are chances to notice vignetting only at the maximum relative aperture where it amounts to 27% (−0.92 EV). By f/2.8 it decreases to 15% (−0.46 EV), and by f/4.0 to 14% (−0.45 EV).

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After passing to the bigger, full frame sensor there far more problems and you can notice them without any problems in photos below.

A7R II, FF, f/2.0	A7R II, FF, f/2.8

A7R II, FF, f/4.0	A7R II, FF, f/5.6

Apparently distortion is not the only category Sigma optics specialists neglected; vignetting should be added to that list too. At the maximum relative aperture brightness loss in frame corners has to be called monstruous as it reaches 72% (−3.64 EV). By f/2.8 you deal with a very high level of that aberration, getting to 57% (−2.44 EV). You also won't have any problems with perceiving that aberration by f/4.0 and f/5.6 where it amounted to, respectively, 43% (−1.65 EV) and 35% (−1.24 EV). By f/8.0 vignetting decreases very slightly when compared to f/5.6, being 34% (−1.20 EV). Further stopping down didn't have any measureable influence on that aberration.

There is a reason of such a weak performance in this category – an unusual vignetting profile, well visible in our graphs below. By f/2.0 image brightness decreases very slowly as you go further from the centre but from 60% of the distance that decrease is accelerated. By f/2.8 this acceleration is visible in a distance of less than 80% from the frame centre and by f/4.0 you can notice it near 90%.

Sony A7R III, JPEG, f/2.0

Below we present averaged out values of brightness loss shown in concentric circles as you move further away from the frame centre. The numerical value for every image, expressed in percents, shows the area limited from the top and right by 100% and from the bottom by the presented curve. The area indicates how much light overall is lost due to the vignetting effect. Please don’t mix these percentages with the values given at the beginning of the chapter because they aren’t directly connected.

Sigma C 35 mm f/2 DG DN - Vignetting