Representative solar Stokes V signals (upper panel) explained by associating their zeros (see legend) with intersections between background (colors) and critical (black) intensities. Vertical dotted lines limit the relevant absorption region (|x_λ| < 1). The medium is weakly magnetized (β = 0.05), and optically thick (T_ν0 = 3) for all cases, but T_ν0 = 1.5 for the three-lobe profile. The values of continuum-to-line opacity (r_c = 0.01) and atomic orientation ( in the right panel or in the other ones) were chosen to ease the explanations.