Flux ratios for the individual progressions of H₂ lines for simulated noisy data with relative flux errors of 0.05. We show the progressions as indicated at the lower or upper right corner of each panel. The line quotient gives the wavelength of the two involved lines for each ratio. They are ordered by increasing wavelength difference between the two lines. In the four upper panels, the black dots show the theoretical flux ratios. The red dots show the flux ratios from the simulated line fluxes. The black lines show the ratios of the dereddened flux (together with the dereddened flux error ratios) forR_V=3.1 and A_V=0.0,0.5,1.0,1.5,3.0. The red and blue lines denote the same for R_V=2.1 and 4.1 for A_V=1.0 and 3.0, respectively. We note that some of the lines are almost identical, which again indicating the degeneracy of R_V and A_V. Three of the four lower panels show contour plots for an increasingly worse fitting of the R_V and A_V values. We show the 68%, 90%, and 95% confidence interval as a black, blue, and yellow line, respectively. The numbers in these lines state the C ~ χ²s for the respective confidence level and are also given in the color bar. The red dot marks the position of the minimum of the distribution, and the black asterisks mark the values chosen for the simulation. In the bottom right panel, we overplot the 160 best-fit Cs for every progression. The progression [1,7] is represented by cyan dots, progression [1,4] is represented by blue triangles, and progression [0,1] is represented by red asterisks. Our retrieved extinction values are marked as a black dot with error bars.