Radiation field scaling factors k(ISRF) in case of selected single-dust models. The black crosses show the values for each combination of cloud FWHM, A_V, and dust model, as listed right of the frame. In cases with A_V > 0, the blue crosses show approximate values at the model boundary, if the effective attenuation is e^{−τ(08 µm)}, using the 0.8 µm optical depth of the external layer.