Surface brightness profiles in i-band of the twenty galaxies shown in Fig. 1. Top: observed surface brightness, azimuthally averaged in radial bins (blue diamonds) and best-fit Sérsic model (black solid curve), as a function of circularised radius. Bottom: residuals between observed and model flux, divided by the model flux. The two different colours correspond to SDSS and GAMA galaxies, as in Fig. 2.