Predicted ratio SFR/L_bol as function of time for the some of the models with exponentially decreasing, delayed, and exponentially rising SFHs (with timescales τ = 10, 30, 300, 3000 Myr indicated), compared to the case of constant SFR. The plots are shown here for BC2003 models with solar metallicity. Same color codes as in Fig. 1. The standard SFR(IR) conversion factor from Kennicutt (1998) is shown by the black dotted line.