Sigma A 35 mm f/1.2 DG DN
8. Vignetting
| A7R II, APS-C, f/1.2 | A7R II, APS-C, f/1.4 |
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In this case some problems can be experienced only in an area close to the maximum relative aperture. By f/1.2 vignetting amounts to 35% (−1.23 EV) and it decreases to 26% (−0.87 EV) on stopping down the aperture to f/1.4. By f/2.0 that aberration becomes imperceptible, reaching just 8% (−0.26 EV).
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After passing to a bigger, full frame sensor there are far more problems and the following photos show it pretty clearly.
| A7R II, FF, f/1.2 | A7R II, FF, f/1.4 |
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| A7R II, FF, f/2.0 | A7R II, FF, f/2.8 |
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Losses of light in frame corners are huge, by f/1.2 they amount to as much as 73% (−3.76 EV), and by f/1.4 they are still 66% (−3.15 EV). It is a very weak performance. It's enough to remind here that the Samyang AF 35 mm f/1.4 FE, a slower and smaller lens, by f/1.4 had a result of 64%, better than the Sigma after a slight stopping down to f/1.4.
By f/2.0 vignetting still remains very distinct, reaching 45% (−1.71 EV). A moderate level of that aberration can be observed only from f/2.8 onwards, with the light fall-off getting to 27% (−0.92 EV), and then it decreases by f/4.0 where we saw a value of 19% (−0.60 EV). Further stopping down didn't have any measureable influence on vignetting.
| Sony A7R II, JPEG, f/1.2 |
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