Sigma A 28-105 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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| A7R IIIa, APS-C, JPEG, 105 mm, f/2.8 | A7R IIIa, APS-C, JPEG, 105 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 12% (-0.37 EV) and it decreases to a completely imperceptible level of 5% (-0.16 EV), when you stop the aperture down to f/4.0.
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After increasing the focal length to 50 mm we got practically identical values that amount to 12% (-0.36 EV) and 5% (-0.14 EV), respectively for f/2.8 and f/4.0.
A very slight increase of the aberration, described here, is observed at 70 mm where, at the maximum relative aperture, it reaches 13% (-0.41 EV), and by f/4.0 it decreases to 5% (-0.14 EV).
The highest, but still pretty low values, you see at the maximum focal length where, by f/2.8, we got a result of 18% (-0.59 EV). On the other hand by f/4.0 it decreased to just 5% (-0.16 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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| A7R IIIa, FF, JPEG, 105 mm, f/2.8 | A7R IIIa, FF, JPEG, 105 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 high zoom ratio makes itself felt here so you deal with huge vignetting, reaching as much as 72% (-3.66 EV). It is one of the highest values we have measured in our tests so far, certainly nothing to boast about.
Still it's worth remembering this vignetting value refers to an angle of view, reaching over 79 degrees, measured by us on an uncorrected file. If you switch distortion correction on and crop the field to the declared value of about 75 degrees, you'll get an image practically devoid of distortion and with much lower vignetting too.
Returning to our measurements on uncorrected JPEG files, by f/4.0 you have to deal with a still high level of 57% (-2.44 EV), by f/5.6 it decreases to 41% (-1.54 EV), and by f/8.0 to 29% (-0.99 EV). Not especially bothersome values are measured only by f/11.0 and f/16.0 apertures, where we got, respectively, 22% (-0.70 EV) and 17% (-0.53 EV).
A significant improvement of the performance is visible after passing to the 50 mm focal length. Here, at the maximum relative aperture, vignetting is 57% (-2.41 EV) and it decreases to 38% (-1.37 EV) when you apply f/4.0. This aberration remains noticeable only by f/5.6 where it reaches 21% (-0.70 EV), and then it becomes negligible because by f/8.0 we measured just 13% (-0.39 EV) and it decreases to 11% (-0.35 EV) on stopping down the lens by an additional f-stop.
Very similar performance can be observed at 70 mm. By f/2.8 brightness loss in frame corners reaches 60% (-2.63 EV), by f/4.0 it decreases to 41% (-1.51 EV), and by f/5.6 to 24% (-0.80 EV). All problems end practically completely by f/8.0 and f/11.0 apertures where we got the following results: 13% (-0.41 EV) and 11% (-0.34 EV).
The maximum focal length shows slight increase of vignetting compared to the situation observed in the 50-70 mm range. By f/2.8 you deal with a level of 62% (-2.78 EV), by f/4.0 it is 43 % (-1.60 EV), and by f/5.6 we got 25% (-0.84 EV). Also at this point all problems end more or less by f/8.0 and f/11.0, where we got the following results: 13% (-0.40 EV) and 11% (-0.32 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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| Sony A7R IIIa, 105 mm, JPEG, f/2.8 |
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