Deviation of fitting to simulated disk r-band magnitude δm_r = m_r,D,sim − m_r,D,fit as a function of the faintness of the disk for objects with m_r < 19.8. Top: multi-band fit. Bottom: single-band fit. Here, and in all successive plots, the subscripts of the axis labels indicate [band] plotted where relevant, as well as [B/D] to indicate bulge or disk component and [fit/sim] to indicate fit or simulated value. Where necessary, we also indicate superscripts M or S1 to indicate multi-band or single-band fitting according to the definition in H13. These plots show that the fainter a disk is within a given bulge, the harder it is to fit, as one would expect. Red horizontal lines show an (empirically chosen) allowed deviation of ± 0.5 mag, and red numbers in the top-left corner indicate the number of objects that violate these limits. The systematic trend reaches this limit when the disk is ~1.5 mag fainter than the bulge. Blue lines show the mean deviation and sigma of the relation (robust mean, clipped at 3 sigma), with the same values for objects at m_r < 18 indicated in orange.