Method d: top panel: luminosity fraction of the outer Sérsic component L_S2 in relation to the total BCG+ICL luminosity L_tot of 49 double Sérsic BCGs. That is column (8) in Table 4 in Kluge et al. (2020). Middle panel: radius r_× beyond which the outer Sérsic component is brighter than the inner. Bottom panel: SB of the transition point SB(r_×). The average absolute BCG+ICL brightness in the bins is coded in the gray shading of each bar.