Top panel: probability in the z−M_B space, P (z,M_B | I), of the ALHAMBRA galaxy presented in Fig. 3. The white dot marks the best Bayesian redshift and M_B, labelled in the panel. Bottom panel: posterior probability in the z−M_B space, PDF (z,M_B), of the same ALHAMBRA galaxy. The convolution with the source function S(I₀ | I,σ_I) produces the desired posterior in real magnitude I₀. The red solid line in both panels shows the I₀ = 24 limiting magnitude, M_B,lim, and the grey areas mark the accessible volumes in z−M_B space.