Photogeometric redshift of a strongly lensed source, assuming a lens model from the family of Sect. 3.1. The blue histogram was obtained by fitting the lensing data assuming a flat prior on log M_h and log Υ_* and the source population distribution of Sect. 3.2, with no correction for the strong lensing selection. The orange histogram was obtained assuming the full model, including the selection function correction, and using the values of the galaxy population parameters, η, inferred in the experiment as a prior. The green histogram was obtained neglecting observational errors and fixing the values of η to the truth. The dashed vertical line marks the true value of the source redshift.