Mass-to-luminosity and luminosity-to-mass ratios as functions of the age (left panel) and the luminosity-to-mass ratio as a function of the stellar mass M_s (right panel). The masses and luminosities are in solar units, the age is in Gyr. Left panel: In the panel the solid red and blue lines are the M_s/L_V and L_v/M_s ratios, respectively, for an infall model of asymptotic mass of 10¹⁰ M_⊙ calculated by the authors (see Chiosi et al. 2023, and references), while the black dots along each line are the same, but for a SSP with solar chemical composition taken from the Padova library (Tantalo 2005). The straight lines are the best fit of the relations. Right panel: M_s/L_V ratio for two infall models with different masses. For each case the stellar mass increases along each curve from left to right. The two straight lines are the best fit of the data (see text for more details).