NaI D doublet lines in our NLTE and LTE model spectra. Top: HET HRS comparison spectra (R = 65 000). The solid black line indicates the position centred between the two line cores and the dashed lines indicate the boundaries of the central 12 Å band. The black points indicate the observed core absorption of the lines. Bottom: Subaru HDS comparison spectra (R = 45 000). The shaded areas indicate the narrow (0.75 Å), medium (1.5 Å), and wide (3.0 Å) passbands used in the analysis.