Venus Optics LAOWA STF 105 mm f/2 (T3.2) review - Vignetting

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Venus Optics LAOWA STF 105 mm f/2 (T3.2)

9 August 2016

Arkadiusz Olech

8. Vignetting

First let’s take care of vignetting on the smaller sensor of the Nikon D7000 – appropriate thumbnails can be found below.

Nikon D7000, f/2.0	Nikon D7000, f/2.8

The small sensor is not a challenge for the Laowa 2/105. At the maximum relative aperture the vignetting is slight, amounting to 18% (-0.56 EV). After stopping down the aperture to f/2.8 you are able to eliminate the problem almost completely with the brightness loss of just 10% (−0.30 EV).

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Now let’s check what happens if you progress to a far more demanding full frame.

Nikon D3x, f/2.0	Nikon D3x, f/2.8

Nikon D3x, f/4.0	Nikon D3x, f/5.6

The full frame sets much higher standards and our measurements reflect that simple truth. The light fall-off in the corners, visible at the maximum relative aperture, reaches 34% (−1.21 EV). It is a significant level. After stopping down the aperture the vignetting decreases but, in our opinion, that effect is not as strong as it should be. By f/2.8 that aberration reaches 22% (−0.71 EV) and by f/4.0 it amounts to 17% (−0.55 EV). The vignetting level remains visible by f/5.6 where we got 14% (−0.42 EV). Only after employing the f/8.0 aperture it disappears completely, decreasing to 10% (−0.30 EV).

We also checked the influence of the second aperture on the vignetting results, the one equipped with as many as 14 blades. The appropriate thumbnails are shown below.

Nikon D3x, f/2.0, T4.0	Nikon D3x, f/2.0, T5.6

The T4.0 aperture means brightness loss of 17% (−0.54 EV) so, within the margin of error, exactly the same as you observed by f/4.0. When you progress to T5.6 the vignetting decreases to 7% (−0.21 EV) - a lower level than the one we got by f/5.6.