Left panel: spectroscopic vs. photometric redshifts for the 21 cluster fields. Outliers, objects for which |Δz|> 0.15, are marked in red. The outlier fraction is 3.5%, the scatter of the remaining objects is σ_z  =  0.029. Right panel: scatter in Δz as a function of K_s-band magnitude, for sources with 0.5 <  z_spec <  0.7. Quiescent and star-forming galaxies are marked in red and blue, respectively. The source detection limits of the 21 K_s-band stacks are indicated.