Impact of the aperture corrections of the D4000_n index on the bimodality-diagnostic plane D4000_n vs. absolute magnitude M_r, for the SDSS sample with S/N ≥ 10. Panels (a) and (b) and the main plot of panel (c) are analogous to Figs. 6 and 7. The side-panel of panel (c) displays the projected distributions in D4000_n for the original fiber D4000_n (filled pink and dark red histogram) and for the aperture-corrected D4000_n (black empty histogram). The dotted horizontal lines mark the position of the minima of the two distributions, respectively.