Sigma A 50 mm f/1.2 DG DN
8. Vignetting
| A7R IIIa, APS-C, f/1.2 | A7R IIIa, APS-C, f/1.4 |
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At the maximum relative aperture vignetting can be noticed as it reaches 29% (−0.99 EV), but it's not especially high. On slight stopping down, by f/1.4, this aberration decreases to 20% (−0.65 EV). All problems end completely by f/2.0, where vignetting decreases further to a quite imperceptible value of 9% (−0.27 EV).
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After passing to the bigger full frame sensor vignetting becomes much more bothersome and photos, shown below, prove that much very clearly.
| A7R IIIa, FF, f/1.2 | A7R IIIa, FF, f/1.4 |
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| A7R IIIa, FF, f/2.0 | A7R IIIa, FF, f/2.8 |
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The loss of light at the maximum relative aperture is really significant as it reaches as much as 68% (−3.26 EV). It is a higher result than 63% presented by the rival Sony. We are not surprised, though, that the Sigma lost in this category – it's enough to remind yourself mechanical vignetting problems from the previous chapter.
Brightness loss in the frame corners decreases slightly by f/1.4 where it amounts to 61% (−2.76 EV). By f/2.0 we got a result of 45% (−1.72 EV), by f/2.8 it was 35% (−1.24 EV), by f/4.0 we measured 28% (−0.96 EV), and by f/5.6 we got a value of 25% (-0.85 EV). Further stopping down had a very slight influence on the vignetting results.
| Sony A7R IIIa, JPEG, f/1.2 |
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