Comparison between the photometric redshifts from FT12 and the spectroscopic redshifts measured in this study. The error bars in z_phot represent the range of 90% significance. The error bars in z_spec are not appreciable, and the median value is 3 × 10⁻⁴. The colour code represents the R_C magnitude. In the bottom left panel, the difference between z_phot and z_spec divided by z_spec against z_spec is plotted. Dashed lines represent the limit in the outlier definition (see Sect. 6.1) and empty red circles represent the outliers. Because of the scale of the ordinate axis, there are points beyond the range of visualization. In the bottom right panel, the distribution of z_sup is shown.