Tests of SPF extraction from a 70° inclined simulated disk surface with different extraction zones. Top: The extraction zone is centered on the ring and its width increases. Bottom: The extraction zone is 2 au wide and its radial position increases. Extraction zones are shown as sets of two colored ellipses on the disk image, and corresponding SPF are plotted with the same color. We show the limb brightening corrected SPF in full color, and the uncorrected one in faint color. The theoretical intrinsic dust SPF is displayed in a dotted black line.