Black dots: all the galaxies in the CANDELS GOODS-South field; red dots: galaxies in the deepest region (HUDF). The purple big squares indicate galaxies with robust spectroscopic redshift in the range 3.5 ≤ z ≤ 7.5. The strict completeness mass vs. redshift for a magnitude limit of H₁₆₀ = 26.0 (dark green). This curve has been derived from the maximally old galaxies in our synthetic library, corresponding to a formation redshift z_form = 20, an E(B − V) = 0.1, metallicity of 0.2 Z_⊙ and a declining SFH with timescale τ = 0.1 Gyr. The light-green curve shows the completeness-corrected limit corresponding to the shallower pointings in the GOODS-South and UDS fields (H₁₆₀ = 26.0), while the blue curve represents the corresponding limit for our deepest area, the HUDF field (H₁₆₀ = 28.0), once the mass limit has been extended taking into account the suitable correction for the M^∗/L distribution. For comparison, the magenta curve (dashed) is the completeness limit in mass in the ERS field derived by Santini et al. (2012a) which corresponds to K = 25.5.