Spectral synthesis results for two galaxies in our samples. a) An early-type galaxy, CIG 257; and b) a late-type galaxy, HCG 49b. The top-left plot in each panel shows the synthetic spectrum (red curve), plotted over the observed spectrum (black curve) normalized by the flux at λ =  4550Å; the bottom-left plot shows the residual spectrum (the difference between the observed and the synthetic continuum spectra), with the green regions representing the mask used; the top-right plot shows the percentage contribution of the light-weighted population vector (x [%] ), and the bottom-right plot the percentage contribution of the mass-weighted population vector (μ [%]  in logarithmic scale), as calculated in each of the three different SSP age groups: young (blue bar), intermediate (yellow bar), and old stellar population bins (red bar).