Summary of the precision and accuracy study. Left panel: precision analysis. σ_age as a function of the age bin size is shown for the four open clusters (black symbols) and the seven synthetic clusters (coloured symbols). For each cluster, four points indicating the measured σ_age for the XL, L, M, and S bins are connected with a line. The three sequences of σ_age for the synthetic clusters correspond to clusters simulated with a different number of stars with M_G = 4.1: ≃350, ≃2000, and ≃14 000. The two sequences of σ_age for the open clusters refer to solutions obtained with two mother CMDs with different unresolved binary star characteristics: q01b03_120M_MG5 (dashed line and open symbols) and q01b07_81M_MG5 (solid line and filled symbols). Right panel: accuracy analysis. The relative error of the age determination is represented as a function of age. Only the synthetic clusters are shown. Clusters with different numbers of stars are depicted in different colours, as labelled. The size of the bins used for each measurement is represented with the corresponding letters.