Analysis of strong saturated line 5183.6 Å. Top: comparison, averaged in metallicity bins of 0.1 dex, of the line χ² fitting values (in logarithmic scale) for different local normalisation intervals (Δλ_norm ∼ 6 Å, 10 Å, 13 Å, 15 Å, 23 Å, 70 Å; taking the shortest interval as a reference, which corresponds to two times the FWHM of the line in a solar-type star, approximately). Bottom: same analysis comparing the derived abundance values.