Retrieved ages, metallicities, dust extinctions and velocity dispersions as a function of the mean S/N of the input spectra. Blue-filled circles represent the differences, averaged over all the computed simulations (i.e. 10×13 models), between the ouptut and the input mass-weighted ages, mass-weighted metallicities, dust extinctions and velocity dispersions (from top to bottom); blue vertical bars are the median absolute deviations (MAD) on all the computed simulations; grey points are the differences derived from each individual simulation; yellow shaded regions in each panel indicate the minimum S/N from which the accuracy of the input retrieving is better than 10%.