Lens review
2007-09-27
Sigma 100-300 mm f/4 DG EX APO IF HSM
8. Vignetting
We did not notice any problem with vignetting either. At 100 mm and f/4.0 the light fall off in the corners of the frame was only 12% (-0.36 the value of the diaphragm) and when we stop down the lens to f/5.6 it drops to 2%.
The situation at 200 mm is ideal. Even at wide open aperture the vignetting is almost invisible (8%) and at f/5.6 it decreases almost to zero.
The slight problem, although it is still diminutive, would be at the 300 mm focal length. At f/4.0 the light fall off in the corners of the frame is 15% (-0.46 the value of the diaphragm). When we decrease the diaphragm by one stop the failure almost disappears (5%).
