Upper left: original velocity map derived from the shifts of the line wing of Fe I 630.15 nm for AR 10923 at θ ≈ 8°. The coordinates are in arcsec relative to disc center. The large inlay is a magnification of the black box. The values along the back slice in the box are plotted in Fig. 4. The other three maps show the velocity map with varying stray-light fractions: α = 0.20 (upper right), α = 0.40 (lower left), and α = 0.60 (lower right). The width of the Gaussian is σ = 2″ in all cases.