Comparison of the normalisation quality when different wavelength regions are analysed. Top panel: spectra computed in the 4200–5800 Å (black), 4000–5800 Å (purple), 3780–5800 Å (red), 3780–6750 Å (yellow) wavelength regions are shown. The bottom panel shows the differences between the spectrum computed in the 4000–5800 Å range and those computed in the other wavelength regions as indicated by the same colours as in the top panel.