Sigma A 20 mm f/1.4 DG DN
8. Vignetting
| A7R III, APS-C, f/1.4 | A7R III, APS-C, f/2.0 |
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At the maximum relative aperture vignetting is noticeable, reaching 34% (−1.20 EV). All problems end by f/2.0, with results decreasing to 16% (−0.50 EV). What's more, by f/2.8 it drops even to 12% (−0.37 EV). Further stopping down of the aperture doesn't have any measureable influence on vignetting.
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After passing to the bigger full frame sensor there are more problems and they are clearly visible in photos below.
| A7R III, FF, f/1.4 | A7R III, FF, f/2.0 |
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| A7R III, FF, f/2.8 | A7R III, FF, f/4.0 |
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Compared to its predecessor, the new version of the Sigma 1.4/20 is smaller, with a possibility of using traditional filters. It also contains more optical elements and is dedicated for mirrorless cameras so its telecentricity challenges are greater. All these factors made me think that indeed its vignetting problems might be more pronounced and let's remind here that the reflex camera variant had vignetting of 65% so −3.02 EV. That's a lot.
We are not surprised that loss of light at the maximum relative aperture is really huge, reaching as much as 72% (−3.68 EV). Vignetting can also be perceived without any problems by f/2.0 where it amounts to 56% (−2.38 EV). By f/2.8 you can still notice its influence as its result gets to 40% (−1.46 EV). By the f/4.0 aperture and higher the aberration, described here, reaches 32% (−1.11 EV).
| Sony A7R III, JPEG, f/1.4 |
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