Line profiles and bisectors on an absolute wavelength scale from 3D and 1D models, exemplified by the medium-strong Fe II 643.26831 nm line in the ‘K2 V’, ‘G1 V’, ‘F7 V’, and ‘F3 V’ models (in rows from top down). Leftmost column: spectra from the full stellar disks, followed by columns for μ = 1, 0.79, 0.41, and 0.09. Rightmost column: vertical bisectors for the 1D profiles confirm that the line is unblended, enabling placement of the 3D bisectors on an absolute wavelength scale (now converted to velocity units). The red bisector curves are expanded tenfold relative to the intensity profiles; their axes are at the top.