Departure coefficient-vertical optical depth distributions in the 3D hydrodynamic model atmospheres shown in Fig. 1. Darker shading indicates a larger density of grid-points. The departure coefficients of the lower and upper levels of the α line are shown. The departure coefficients of the heavily populated ground level (n = 1) always stay close to unity, while the departure coefficients of the more excited levels (n > 3) and the ionised state (H II) roughly follow those of the n = 3 state.