Distribution of the opacity bins in optical depth and wave-length for the four stars. Similarly to Fig. 8, each coloured dot corresponds to one ODF substep. The wavelength separators are identical for all stars (λ < 300, ∈ [300, 500], ∈ [500, 700], ∈ [700, 1000], ∈ [1000 – 2000], and > 2000 nm). All values within one wavelength range are shown in the same colour. The τ-separators are selected from the optimal combinations found in Sect. 5.1 for each star: log τ = {−1.9, −5, −7} for the F3V star; log τ = {0, −2.5, −5} for the G2V; log τ = {−0.2, −3, −5} for the K0V; log τ = {0.3, −0.8, −2.5} for the M2V.