Left panels: scatter plots between the spectroscopic redshift (z_s) and the photometric redshift (z_p). Right panels: close-up of the distribution of the redshift differences z_p − z_s for | z_p − z_s |  < 0.03. The grey colour is used when the photometric redshifts are computed using the BPZ code, while the black colour is used when the photometric redshifts are assigned randomly. In the upper panels the random photometric redshifts are assigned using a Gaussian probability distribution with the spectroscopic redshift as the centre and 0.0025 as the Gaussian width. In the lower panels the random photometric redshifts are assigned using a Lorentzian probability distribution, with a width of 0.00244 (see text for full description).