Heatmaps showing the integrated absolute difference (ΔArea; Eq. (1)) between the convolved and unconvolved SB curves. The left panels show variations with size distribution slope (q) and minimum grain size (s_min) at a fixed geometry for inclinations of 50°, 70°, and 80°. The right panels display the variations with the disc opening angle and inclination for s_min = 2, 10, and 30 micron.