Viltrox PFU RBMH 85 mm f/1.8 STM review - Vignetting

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Viltrox PFU RBMH 85 mm f/1.8 STM

14 October 2019

Arkadiusz Olech

8. Vignetting

First let's check the vignetting performace at the smaller APS-C sensor – below you can find appropriate thumbnails we got in the crop mode with the help of the Sony A7R II camera.

A7R II, APS-C, f/1.8	A7R II, APS-C, f/2.0

The brightness loss in frame corners is not bothersome practically at all because even at the maximum relative aperture it reaches just 12% (−0.38 EV). By f/2.0 it decreases to 11% (−0.33 EV) and by f/2.8 it becomes completely imperceptible, amounting to 5% (−0.16 EV).

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As the rear element of the Fuji X model is more encased, with a smaller gap, and the area next to the mount looks different than in the Sony version, we suspected, not without a reason, that the results of the Viltrox's vignetting test, performed on the Fuji X-T2, might be different.

Let's look at thumbnails below.

Fuji X-T2, APS-C, f/1.8	Fuji X-T2, APS-C, f/2.0

Our suspicions were right. At the maximum relative aperture you lose 28% (−0.95 EV) in frame corners. That value decreases to 23% (−0.75 EV) after passing to f/2.0 and then it drops to an imperceptible level of 10% (−0.31 EV) on stopping down to f/2.8. It is clear vignetting is a bit more pronounced than in the case of the Sony but still its level cannot be described as bothersome.

After passing to the bigger, full frame sensor, there are more problems and the situation is clearly visible in photos, presented below.

A7R II, FF, f/1.8	A7R II, FF, f/2.0

A7R II, FF, f/2.8	A7R II, FF, f/4.0

At the maximum relative aperture you have to take into account the loss of 48% (−1.86 EV) of light in frame corners. It's a lot but the result still remains significantly better than 58% we got in the test of the Sony. By f/2.0 vignetting decreases to 43% (−1.64 EV), and by f/2.8 to 27% (−0.92 EV). The problem becomes slight by f/4.0 and f/5.6 apertures where we got, respectively, 15% (−0.47 EV) and10% (−0.31 EV).

Sony A7R II, JPEG, f/1.8