Major- and minor-axis disk profiles (upper and middle rows) showing the deviations from Sérsic functions due to projection effects. Solid upper curves are for B-band dust-free images, dashed curves are for corresponding variable-index Sérsic fits, while absolute residuals (simulation − fit) are represented by solid lower curves. The fits were made by fixing the position of the intensity peak of the fitted image to the geometrical centre of the map. The cuts were taken parallel and perpendicular to the major-axis of the dust-free disk images, through their geometrical centres, at inclinations 1 − cos(i) = 0.3,0.7,0.9 (i = 46°,73°,84°). Lower row: corresponding relative residuals at the same inclinations as the profiles. The red lines show radial and vertical cuts through the geometrical centre of each image.