Top panel: photometric redshift accuracy σ_z versus fraction of catastrophic errors η. Bottom panel: completeness versus purity of the z_phot catalogues. In both panels, filled squares are for the whole population, whereas empty circles are for the red-sequence galaxies only. Error bars were estimated by repeating the measurements on 100 randomly-picked training and testing samples. Notice that the worst values are for RXC J2011, which was observed only in two filters.