Left column: the ratio of the thick to thin disc face-on surface density – Σ_T/ Σ_t – for the four axial bins of ESO 533-4. Each data point corresponds to a fitted value obtained using a non-symmetrised PSF rotated φ degrees clockwise with respect to the direction indicated by the mid-plane of ESO 533-4. The grey horizontal lines indicate the Σ_T/ Σ_t values obtained in the fits made using the symmetrised PSF (same as in the bottom panels in Fig. 5). Right column: same as the left column but for NGC 6010 and with Σ_T/ Σ_t values indicated by the horizontal grey line corresponding to Fig. 6.