Faint-end slope α_S of the LF derived in this work [M(I_E) ≤ −12; big filled cyan circle] compared to the values of the analogous Schechter parameters α available in the literature in different photometric bands for the Perseus cluster (green circles, references given in the text), for the Coma cluster (red boxes, taken from the compilation of Milne et al. 2007), the Virgo cluster (blue triangles, from the compilation of Ferrarese et al. 2016), and for the composite LF of clusters of Popesso et al. (2005, black hexagons, double Schechter functions, measured using two different background subtraction techniques within 0.5 Mpc). Empty symbols are for LF of the whole cluster, and filled symbols for the core region, as in the Euclid field.