RFF shown as a function of the r′-band apparent magnitude for the Fornax cluster early-type galaxies in our catalog. The black points show the galaxies which have clear structure (for example a bar or an inner disk) differing from the single Sérsic model, and the red points are smooth early-type galaxies. The points on the left side of the vertical dashed line are giant galaxies (M_r′ <  −18.5 mag) not included in our final catalog. The horizontal line shows the RFF = 0 level. The systematic shift of RFF from zero in the high luminosity end can be understood as galaxies starting to differ from Sérsic profiles, whereas the increasing scatter in the low luminosity end is mostly explained by decreasing signal-to-noise.