Values of R_Veff as a function of A_Veff (panels a and c) and the corresponding values of A_Vdir and R_Vdir (panels b and d) for a simulated spiral galaxy (left plots) and a simulated elliptical galaxy (right plots). A_Vdir and R_Vdir were calculated from only the direct flux component, ignoring the scattered flux component. Different colors denote different observation angles, from 0° (face-on) to 90° (edge-on). An aperture radius of 20 kpc was used. The galaxy dust density has been normalized so that the total optical depth along the R axis is τ_VR = 5. The dashed black line reflects the true extinction R_VZubko.