This paper aims to determine and compare the vignetting effect (luminance radial falloff) of two identical SIGMA lenses mounted on two identical cameras (same manufacturers, models and references). For the largest aperture (f/2.8), the average luminance loss of the two devices is 66%, at the periphery of the fisheye, with a difference of loss of 0.5%. For each aperture, the difference between root mean square errors (RMSE) of vignetting curve of each device is always less than 0.7%. Vignetting effect is thus similar for the two devices.