Lens review

Sigma 17-50 mm f/2.8 EX DC OS HSM

8. Vignetting

Let’s check how the Sigma 17–50 mm f/2.8 EX DC OS HSM deals with the vignetting. We can assess it looking at the miniatures below, taken by f/2.8 and f/4.0 apertures and at 17, 30 and 50 mm focal lenght.

At the widest angle and maximum relative aperture the vignetting will be the most bothersome. It amounts there to 38% (-1.37 EV) and can be noticed without any problems in real life photos. The Sigma fares a bit worse here than the Nikkor 17-55 mm, which reached the level of 33% ,and a bit better than the Canon 17-55 mm, which lost as much as 40 % of light. In the case of the Sigma the vignetting decreases quite slowly on stopping down the aperture. By f/4.0 it is 22%, by f/5.6 it amounts to 18%. Further stopping down doesn’t influence the vignetting any longer – it keeps a fixed level of 17-18%.

In the middle of the focal lengths range the problems with vignetting are the least significant. By f/2.8 the light fall-off in the frame corners amounts to 23% (-0.76 EV) and it decreases to 13% by f/4.0. On further stopping down we see a very slight influence on vignetting once again – by f/5.6 it is 12% and by f/8.0 – 11%.

At 50 mm we see the increase of this aberration. At the maximum relative aperture our measurements show that the lens loses in the corners 31% of light (-1.08 EV). Fortunately in this case the stopping down is very efficient when it comes to vignetting correction. By f/4.0 the brightness loss in the frame corners reaches 14% and by f/5.6 it decreases to an imperceptible level of 9%.