Example a Sérsic profile μ(R^⋆) with a η = 3 and an effective radius R_eff = 3″ (solid line). Top panel: vertical dashed lines correspond to the radii enclosing 40, 50, 60, 70, 80 and 90% of , and horizontal lines depict the corresponding mean surface brightness ⟨I_i⟩ therein. Middle panel: contribution to as a function of R^⋆ (i.e., integrand in Eq. (3)) normalized to the maximum flux (F(R^⋆)/F_max. Bottom panel: light growth curve L(R^⋆)/L_tot of the profile. It can be seen that, although the innermost points (R^⋆/R_eff ≤ 0.25) show the highest intensity, they are nearly irrelevant in terms of their contribution to the total luminosity.