Mean value in bins of constant (NUV − r) and (r − K) of different parameters describing attenuation of starlight from dust for the model SEDs described in Sect. 5. Top-left panel: galaxy inclination 1 − cosθ. Top-right panel, V-band attenuation optical depth suffered by stars younger than 10⁷ yr . Bottom-left panel, V-band attenuation optical depth suffered by stars older than 10⁷ yr . Bottom-right panel, slope of the optical attenuation curve in the diffuse ISM, , measured from a power law fit to the model attenuation curves in the range 0.4 ≤ λ ≤ 0.7  μm.