Bias and uncertainty of the photometric cluster redshifts z_λ estimated by comparing to high-quality spectroscopic cluster redshifts z_spec. Black points refer to 9522 clusters with high-quality spectroscopic redshifts (see Sect. 8). The catalogs were merged as described in Sect. 4.1.1. The red line is the running median, and the red shaded regions give the uncertainty δz_λ taken as the 16th and 84th percentiles of the distribution. In the left panel, the continuous red line is the redshift bias Δz_λ, and the dashed lines give the redshift uncertainty δz_λ. The right panel shows the absolute errors normalized by 1 + z_spec, which is proportional to the line-of-sight velocity v (Eq. (6)).