Line profile comparison between observed and model spectra for four example lines Na I 5897, Mg I 5185, Ca I 6163, Fe I 5384 (top to bottom; panels span velocity ranges ±20, ±40, ±30, and ±30 km s⁻¹, respectively), and for model spectra for SME LTE, SME NLTE, and CO⁵BOLD calculations (left to right). For each panel, the upper plot shows observed IAG FTS spectra as solid lines and model spectra as dashed lines. Lower plots show data/model ratios on a logarithmic scale. Five limb positions, μ = 0.2, 0.4, 0.6, 0.8, 1.0, are shown for each set of spectra. Darker color is used for spectra taken closer to disk center.