Sigma C 28-70 mm f/2.8 DG DN
8. Vignetting
| A7R IIIa, APS-C, JPEG, 28 mm, f/2.8 | A7R IIIa, APS-C, JPEG, 28 mm, f/4.0 |
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| A7R IIIa, APS-C, JPEG, 50 mm, f/2.8 | A7R IIIa, APS-C, JPEG, 50 mm, f/4.0 |
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| A7R IIIa, APS-C, JPEG, 70 mm, f/2.8 | A7R IIIa, APS-C, JPEG, 70 mm, f/4.0 |
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At the 28 mm focal length the problem practically doesn't exist. By f/2.8 vignetting reaches just 14% (-0.43 EV) and it decreases to a completely imperceptible level of 6% (-0.18 EV), when you stop the aperture down to f/4.0.
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After increasing the focal length to 50 mm the values are even better, amounting to 11% (-0.34 EV) and 5% (-0.16 EV), by f/2.8 and f/4.0 respectively.
A very slight increase of the aberration, described here, is observed at 70 mm where, at the maximum relative aperture, it reaches 15% (-0.47 EV), and by f/4.0 it decreases to 5% (-0.14 EV).
On the APS-C sensor the tested Sigma doesn't show practically any problems with vignetting. What about the full frame? Let's find out.
| A7R IIIa, FF, JPEG, 28 mm, f/2.8 | A7R IIIa, FF, JPEG, 28 mm, f/4.0 |
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| A7R IIIa, FF, JPEG, 50 mm, f/2.8 | A7R IIIa, FF, JPEG, 50 mm, f/4.0 |
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| A7R IIIa, FF, JPEG, 70 mm, f/2.8 | A7R IIIa, FF, JPEG, 70 mm, f/4.0 |
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A difficult combination of the wide angle and good aperture fastness, offered by the lens with so small physical dimensions makes itself felt here with full power so you deal with huge vignetting, reaching as much as 67% (-3.23 EV). Small wonder the bigger Tamron fared a bit better here, with a value of 62%.
By f/4.0 you have to deal with a still high level of 49% (-1.97 EV), by f/5.6 it decreases to 33% (-1.14 EV), and by f/8.0 to 21% (-0.68 EV). Further stopping down of the aperture doesn't have a bigger influence on this aberration – you can gain just one percentage point.
After passing to the 50 mm focal length you see a significant improvement of the performance. At the maximum relative aperture vignetting amounts to 59% (-2.58 EV) and it decreases to 39% (-1.42 EV), when you employ f/4.0. By f/5.6, f/8.0, and f/11.0 apertures we got respectively: 27% (−0.90 EV), 21% (−0.67 EV), and 16% (−0.50 EV).
Very similar performance you can observe at the 70 mm focal length. By f/2.8 the brightness loss in frame corners reaches 61% (-2.75 EV), by f/4.0 it decreases to 41% (-1.54 EV), and by f/5.6 to 28% (-0.95 EV). All problems ends practically completely by f/8.0 and f/11.0 where we got the following results: 16% (-0.52 EV) and 12% (-0.36 EV).
| Sony A7R IIIa, 28 mm, JPEG, f/2.8 |
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| Sony A7R IIIa, 50 mm, JPEG, f/2.8 |
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| Sony A7R IIIa, 70 mm, JPEG, f/2.8 |
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