Selection effects on CMFs due to detection incompleteness. The initial CMF is shown as a black line (Schechter function with power-law index β=−2 and truncation mass M_C = 10⁴ M_⊙). Top panel: CMFs for artificial clusters of various ages (see legend) in the B3 field, showing results for CBR≥1.0 (dashed lines) and CBR≥0.4 (solid lines). Bottom panel: CMFs for clusters of log(t/yr) = 9 age, measured in the B1–B5 background fields at different radial distances from the M 31 centre, assuming the detection threshold CBR≥0.4. Results are based on artificial clusters with half-light radii of R₅₀ = 0.25″−1.00″.