Tokina Fírin 20 mm f/2 FE MF review - Vignetting

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Tokina Fírin 20 mm f/2 FE MF

16 November 2017

Arkadiusz Olech

8. Vignetting

First let’s check how vignetting looks on the smaller APS-C sensor– appropriate thumbnails you can find below.

A7R II, APS-C, f/2.0	A7R II, APS-C, f/2.8

The brightness loss is clearly visible only at the maximum relative aperture where it reaches 29% (−0.99 EV). By f/2.8 it decreases to 19% (−0.60 EV), and by f/4.0 it is 17% (−0.52 EV). Further stopping down of aperture doesn’t have any measurable influence over this aberration.

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After progressing to the full frame sensor the problems are more serious and there are more of them – let’s glance at photos below.

A7R II, FF, f/2.0	A7R II, FF, f/2.8

A7R II, FF, f/4.0	A7R II, FF, f/5.6

At the maximum relative aperture the vignetting gets to a very high level of 61% (−2.72 EV). It is no end of bad news. The aberration decreases slowly on stopping down, so by f/2.8 it is 52% (−2.13 EV), and by f/4.0 it still amounts to 32% (−1.56 EV), a quite significant level. What’s even worse, further stopping down doesn’t bring any distinct effects because by f/5.6 and f/8.0 the brightness loss in the frame corners remains 31% (−1.55 EV).

Unfortunately the Tokina compares very unfavourably with rival lenses. For example the Nikkor 1.8/20 at its maximum relative aperture, which is even faster than that of the tested lens, had 49% of vignetting.

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.

Tokina Fírin 20 mm f/2 FE MF - Vignetting