Variations with N_{H mλ}, in five separate clouds, of the fraction of the total column density in each phase (upper panel, H i in black, DNM in red, CO in blue) and of the fraction of the total H₂ column density that is CO dark (lower panel). Downward and upward triangles, stars, crosses, and circles refer to Musca, Cham I, Cham II+III, Cham East I, and Cham East II, respectively. The dark to light grey curves correspond to the clouds in the same order. The shaded areas cover the chosen uncertainty in DNM composition from 50% to 100% H₂. The dotted and solid error bars give the standard deviations and errors on the mean in each N_H bin; they are shown for only one cloud and the fully molecular DNM case.