Sigma C 20 mm f/2 DG DN
8. Vignetting
| A7R III, APS-C, f/2.0 | A7R III, APS-C, f/2.8 |
|
|
In this case you can spot vignetting only at the maximum relative aperture, where it amounts to 30% (−1.03 EV). By f/2.8 the aberration decreases to 17% (−0.52 EV), and by f/4.0 it drops to 14% (−0.44 EV)
Please Support UsIf you enjoy our reviews and articles, and you want us to continue our work please, support our website by donating through PayPal. The funds are going to be used for paying our editorial team, renting servers, and equipping our testing studio; only that way we will be able to continue providing you interesting content for free. |
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
After passing to the full frame sensor there are far more problems; images, presented below, show it pretty clearly.
| A7R III, FF, f/2.0 | A7R III, FF, f/2.8 |
|
|
| A7R III, FF, f/4.0 | A7R III, FF, f/5.6 |
|
|
At the maximum relative aperture vignetting reaches a monstrous level of 77% (−4.27 EV). I am always irritated when, with such a high vignetting level, somebody suggests the lens in question should be considered slower than declared by the producer. In this case, however, I think Sigma went over the top; indeed they should have made this lens slower aperture-wise or maybe simply a tad bigger. That way they would have avoided such a serious slip-up.
Vignetting remains on a very high level also after stopping down the aperture: by f/2.8 you get a level of 66% (−3.08 EV), by f/4.0 it reaches 52% (−2.10 EV), and by f/5.6 the result amounts to 40% (−1.48 EV). Further stopping down doesn't cause any measureable decrease of this aberration.
| Sony A7R III, JPEG, f/2.0 |
 |
