Left: [IRAS] versus L₈ for local ISO and AKARI galaxies (filled blue dots). The GOODS-Herschel galaxies are shown in the background with lighter orange symbols (same points as in Fig. 6) together with their median (black solid line) and 68% dispersion (black dashed lines). The light blue line shows the locus traced by the CE01 SED library. Right: histogram of the IR8 ratios for the local galaxy sample (blue, upper panel) and GOODS-Herschel sample (orange, bottom panel). The solid curves show Gaussians fit to the distributions. The vertical grey lines indicate the median (solid) and 68% dispersion (dashed) for the full samples (as in Eqs. (3), (2)).