The comparison between the vignetting effects of the four devices (CAM# 1FE# 1, CAM#2FE#2, CAM#1FE#2 and CAM#2FE# 1) was realized on the basis of white squares only, in calculating differences of RMSE, for four apertures.
Generally, the evaluation of lens vignetting aims at determining a filter to apply to HDR pictures, in order to counterbalance the light fall off observable from the center of the picture to its periphery.
where[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII]is the filter determined for the aperture A[v.sub.i] and [??] is the approximated vignetting function for this same aperture A[v.sub.i].
This filter is applied to HDR pictures to correct vignetting errors, as follows:
where [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] is the vignetting corrected HDR picture, [L.sub.HDR] is the original HDR picture, and [??] is the filter determined for the aperture A[v.sub.i] used to take the picture.
Figures 12 and 13 present the vignetting values determined respectively for CAM#1FE#1 and CAM#2FE#2, using (6).
Figure 15 presents the differences of RMSE calculated, for each device, on the basis of white or gray vignetting values.
Figure 16 presents the RMSE of the vignetting curves approximated for each tested aperture of each device and calculated as in (7).