Comparison between the photometric observations and the mean synthetic SED built using only the BC03 models. The averaging of the photometric data points was done as for Fig. 1 as well as the corrections for extinction using the CCM reddening law. The insert presents the average star-formation history − for three broad metallicity bins − of all galaxies in the sample used to compute the mean synthetic SEDs, for both the BC03 model shown in this figure, and the M2013 models shown in Fig. 1.