Relative deviations of the new, exact RF-based (solid curves) and old Kompaneets-based (dashed curves) spectra from the best-fit diluted blackbodies versus photon energy for hydrogen (top panel) and solar H/He mixture with Z = 0.3  Z_⊙ (bottom panel) low gravity (log g = 14.0) models. Corresponding relative luminosities and the effective temperatures are given at the curves. The vertical dotted line shows the lower boundary of the energy band, where the fitting procedures were performed. For clarity, models with l = 0.1 and 0.5 are shifted up by 0.2 and 0.1, respectively.