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Lens review

Sigma 18-50 mm f/2.8-4.5 DC OS HSM

8 March 2010
Szymon Starczewski

8. Vignetting

Lenses of focal lengths starting at 16-18 mm and ending at 50-85 mm are often troubled by vignetting. Some major flops were recorded here by most manufacturers’ lenses. Small and compact lens body of Sigma in combination with its quite good speed suggests that we won’t avoid problems here either. And that’s the case… 

Sigma 18-50 mm f/2.8-4.5 DC OS HSM - Vignetting



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At the most difficult combination of 18 mm focal length and f/2.8 brightness, the lens loses 51% (-2.05 EV) of light in the corners of the frame. For comparison, Sigma 17-70 recorded vignetting of 40%, identical result recorded Nikkor 18-55 VR. Too bad Sigma 18-50 OS didn’t refer to the good result of Sigma 18-50 mm f/2.8 HSM Macro, which recorded the results of 23%.

With stopping down vignetting falls, but the pace isn’t as fast as we’d like it to be. At f/4.0 the light fall-off in the corners of the frame reaches 34%, at f/5.6 it’s still 27%. Even stopping down to f/8.0 lets us see vignetting, which equals 21% there. The acceptable level of this aberration, reaching 16%, is obtained at f/11.

In the middle of the focal length range it’s not good either. At the maximum aperture vignetting reaches 40% (-1.49 EV). Fortunately, stopping down here helps much more. At f/5.6 the light fall-off in the corners of the frame equals 15% and at f/8.0 this aberration becomes unnoticeable.

The least problems with vignetting we’ll have at 50 mm. There, at the maximum aperture, this aberration reaches the level of 37% (-1.14 EV) and at f/5.6 falls to 18%. At f/8.0 it becomes practically invisible (7%).


Sigma 18-50 mm f/2.8-4.5 DC OS HSM - Vignetting

Sigma 18-50 mm f/2.8-4.5 DC OS HSM - Vignetting