CMF mean intensity at R_max (≈ 120 R_*), for a hot dwarf model with T_eff = 55 000 kK and a large mass-loss rate, calculated with different approximations for the incident intensity, I⁻, and different wavelength regimes. All intensities have been taken from the same iteration step, namely the first step after the detailed CMF-treatment has been initiated. Color-coding – black: complete incident intensity including frequency derivative, as described in the text; red: I⁻ = 0; dark blue (mostly blended by turquoise): I⁻ specified only for lines and continua of significant optical depth, gradient neglected; turquoise: I⁻ specified for all frequencies, but gradient neglected; green: approximate pseudo-continuum, as used in the previous FASTWIND version, and still at highest and lowest wavelengths. Left panel: EUV range between 200 and 300 Å; right panel: frequency range around the C IV resonance doublet in the UV.