Comparison of the diffracted light corresponding to different IO sizes for the same tilt of 25 arcsec. The green curve corresponds to R_IO = 1.662 mm, the yellow curve indicates R_IO = 1.677 mm, the blue curve indicates R_IO = 1.694 mm, and the black solid curve denotes symmetrical case with R_IO = 1.662 mm. Thin black and blue lines denote the coronal signal with vignetting taken into account or the vignetting functions (in the bottom part of the plot).