Comparison of disk-centre Stokes parameter LSD profiles computed using detailed radiative transfer calculations (symbols connected by solid black lines) and the single-line UR approximation (red lines). The dotted blue lines show LSD Stokes I profiles before continuum re-normalisation. Each row displays a different Stokes parameter: I (top), V (middle), and Q (bottom). The columns correspond to increasing magnetic field strengths, ranging from 100 G to 10 kG. In all panels, the magnetic field vector is inclined at an angle of 45° to the line of sight.