Upper and middle panels: scaled flux contribution function C_ν (solid blue), source function S_ν (dash-dotted red), Planck function B_ν (dashed green), and intensity J_ν (dotted cyan) for λ = 8500.36 Å representing the line core (upper panel) and λ = 8500.54 Å in the line wing (mid-panel) of the Ca II IRT line in model #080. The peak at high column mass in the contribution function of the line wing shows that the photospheric flux already dominates at this wavelength but there is still some chromospheric contribution. Lower panel: temperature structure of model #080 and the formation regions of Na I D₂, Hα, and the bluest Ca II IRT line.