Sony FE 35 mm f/1.8
8. Vignetting
| A7R II, APS-C, f/1.8 | A7R II, APS-C, f/2.0 |
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| A7R II, APS-C, f/2.8 | A7R II, APS-C, f/4.0 |
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Small dimensions of the lens mean you can notice distortion already on the smaller detector. At the maximum relative aperture that aberration reaches 33% (−1.15 EV) and then, on stopping down to f/2.0, it slightly decreases to 31% (−1.08 EV). Some chances to spot vignetting you get even by f/2.8 where we got a value of 22% (−0.74 EV). By f/4.0 and f/5.6 you deal with almost imperceptible level of that aberration and in these places we measured, respectively, 16% (−0.50 EV) and 15% (−0.46 EV).
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Now let's check the situation on full frame – appropriate thumbnails are shown below.
| A7R II, FF, f/1.8 | A7R II, FF, f/2.0 |
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| A7R II, FF, f/2.8 | A7R II, FF, f/4.0 |
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| A7R II, FF, f/5.6 | A7R II, FF, f/8.0 |
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As we expected there are a lot of problems here – not only vignetting reaches really huge levels but also that aberration reacts very weakly on stopping down the aperture. By f/1.8 we got a result of 67% (−3.17 EV), and it decreased just slightly to 66% (−3.11 EV) on applying f/2.0 relative aperture. Also by f/2.8 and f/4.0 the brightness loss in the frame corners was very high, and we got in these places the following values: 64% (−2.98 EV) and 61% (−2.76 EV). Further stopping down helps but to a not especially satisfactory degree – by f/5.6 the aberration, described here, reaches 58% (−2.54 EV), by f/8.0 it amounts to 56% (−2.37 EV), and by f/11.0 it decreases to 52% (−2.14 EV). Even by f/16.0 you can talk about a high degree of vignetting because our measurements still showed 49% (−1.95 EV).
It seems that, while taking photos with the help of the Sony FE 35 mm f/1.8, you won't be able to avoid vignetting no matter what aperture value you are going to use.
| Sony A7R II, JPEG, f/1.8 |
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Below we present averaged out values of brightness loss shown in concentric circles as you move further away from the frame centre. The numerical value for every image, expressed in percents, shows the area limited from the top and right by 100% and from the bottom by the presented curve. The area indicates how much light overall is lost due to the vignetting effect. Please don’t mix these percentages with the values given at the beginning of the chapter because they aren’t directly connected.
