Samyang AF 24-60 mm f/2.8 FE
8. Vignetting
| A7R IIIa, APS-C, JPEG, 24 mm, f/2.8 | A7R IIIa, APS-C, JPEG, 24 mm, f/4.0 |
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| A7R IIIa, APS-C, JPEG, 40 mm, f/2.8 | A7R IIIa, APS-C, JPEG, 40 mm, f/4.0 |
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| A7R IIIa, APS-C, JPEG, 60 mm, f/2.8 | A7R IIIa, APS-C, JPEG, 60 mm, f/4.0 |
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At the 24 mm focal length and by f/2.8 vignetting remains practically imperceptible, reaching just 10% (-0.30 EV). Stopping down the aperture to f/4.0 decreases this aberration to 4% (-0.13 EV).
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In the middle of the focal range the situation is even better because at the maximum relative aperture, brightness loss in frame corners reaches just 8% (-0.25 EV), and by f/4.0 it decreases to a negligible level of 2% (-0.07 EV).
At the maximum focal length you return to the values from the other end of the range because by f/2.8 vignetting once again reaches 10% (-0.29 EV), and by f/4.0 it drops to just 1% (-0.04 EV). You also have to remember that JPEG files are distortion-corrected and cropped so their vignetting level is a tad lower than in case of RAW files. Still, we have no intention of showing here all thumbnails and describing in detail results for RAW format. They usually differ only slightly and are by 2-3 percentage points higher than these we mentioned a moment earlier.
At the APS-C/DX sensor the tested Samyang didn't provide any reason to worry, but still we were very curious how the situation changes after passing to full frame. Let's glance at thumbnails presenting images saved as distortion-corrected JPEG files.
| A7R IIIa, FF, JPEG, 24 mm, f/2.8 | A7R IIIa, FF, JPEG, 24 mm, f/4.0 |
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| A7R IIIa, FF, JPEG, 40 mm, f/2.8 | A7R IIIa, FF, JPEG, 40 mm, f/4.0 |
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| A7R IIIa, FF, JPEG, 60 mm, f/2.8 | A7R IIIa, FF, JPEG, 60 mm, f/4.0 |
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At the most demanding combination of the 24 mm focal length and f/2.8 aperture, you have to live with a loss of as much as 47% (-1.84 EV) light in frame corners. It is not a bad result. Many classic journalistic 24-70 mm f/2.8 lenses fared much weaker. Of course you have to remember the fact that this result is after distortion correction and cropping the image to an angle of view of 83.08 deg, a tad narrower than the declared one. When you examine RAW files, with an angle of view of 87 deg, so 3 degrees wider than in official specifications, you find out that the corners of the frame are practically black. Our measurements show that they get only 4-6% of light. In this configuration the lens's image circle is a tad smaller than full frame.
When you return to the JPEG files' measurements, you see that stopping down is not as efficient as you wish it was. At 24 mm and by f/4.0 vignetting reaches 36% (-1.31 EV), by f/5.6 it decreases to 34% (-1.21 EV), by f/8.0 it is 31% (-1.06 EV), by f/11 it drops to 28% (-0.94 EV), and by f/16 to 21% (-0.70 EV).
| A7R IIIa, FF, RAW, 24 mm, f/2.8 | A7R IIIa, FF, RAW, 24 mm, f/4.0 |
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| A7R IIIa, FF, RAW, 40 mm, f/2.8 | A7R IIIa, FF, RAW, 40 mm, f/4.0 |
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| A7R IIIa, FF, RAW, 60 mm, f/2.8 | A7R IIIa, FF, RAW, 60 mm, f/4.0 |
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In the middle of the focal range the situation is a bit better. By f/2.8 JPEG files feature vignetting reaching 33% (-1.18 EV) and on stopping down to f/4.0 its level decreases to 18% (-0.58 EV). This aberration becomes practically imperceptible already by f/5.6 and f/8.0 where we got results of, respectively, 11% (-0.33 EV) and 7% (-0.20 EV).
You have to remember that in the middle of the focal range barrel distortion remains noticeable, so also in this place JPEG files are corrected and cropped. The analysis of RAW files indicated that results are by 3-4 percentage points higher than these presented above.
At the maximum focal length, vignetting is once again a bit higher. In case of JPEG files by f/2.8 we got a level of 37% (-1.32 EV), that decreased to 16% (-0.50 EV) on stopping down the lens to f/4.0. By f/5.6 relative aperture, the problem becomes marginalized with a result of just 4% (-0.13 EV).
At 60 mm distortion is the lowest; small wonder the differences between measurements on JPEG and RAW files are the smallest, reaching just 2-3 percentage points.
To sum up, introducing very high distortion with a spare amount of field of view available means that after the correction the files are devoid of very high vignetting. In this aspect the lens performs sensibly well, showing results noticeably lower than the results of classic 24-70 mm models. Still you have to remember the price you have to pay – different operations on files mean that you have to pump empty pixels and image resolution on the edge of the frame is weaker than in the classic approach, where distortion is corrected as it should be by the lens's optics.
| Sony A7R IIIa, 24 mm, JPEG, f/2.8 |
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| Sony A7R IIIa, 40 mm, JPEG, f/2.8 |
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| Sony A7R IIIa, 60 mm, JPEG, f/2.8 |
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