Example from the FTS atlas of the CLV. The top panel shows the disk-center spectrum with line identifications, the middle panel the limb spectrum (at μ = 0.145), both normalized to the level of the continuum. The bottom panel gives the ratio R between the limb and disk-center spectra. By definition the continuum is represented by the level unity. Amplitudes above unity imply that the limb darkening inside the respective lines is flatter than in the continuum.