Recovered best-fit photometric vs. input redshift (top), accuracy (middle), and outlier fraction (bottom) for 27 000 simulated sources with spectral slope of 0.05 ≤ β ≤ 2 and optical brightness of r′ = 17−19 mag. The pink circles indicate the location of three blazars in our sample with known redshift, PKS 0332-403 (z_spec = 1.351, Bergeron et al. 2011), OM 235 (z_spec = 1.549), and CRATES J1312-2156 (z_spec = 1.491, Ackermann et al. 2012), as well as that of PKS 0537-286 (z_spec = 3.104, Wright et al. 1978), a LAT-non-detected blazar with available GROND and UVOT photometry. The green area in the middle panel corresponds to the forbidden parameter space where z_phot > 0. Systematics are visible at z_phot < 0.8. The large majority of the fits have χ² < 30 (for typically 10 d.o.f.) with the exceptions shown in light grey. The inset in the top panel displays the results if only solutions with P_z > 90% are selected.