Relation of the slope of the faint end α of the luminosity function and the wavelength at which the luminosity function has bean measured. The large filled dots show values derived within a footprint comparable to the one used in the VESTIGE survey, and small open squares show values measured within a much more limited region of the cluster. The slope of the luminosity function in the different photometric bands was taken from Boselli et al. (2016c) in the UV, Sandage et al. (1985), Trentham & Hodgkin (2002), and Sabatini et al. (2003) in the B, Ferrarese et al. (2016) in the g, Lieder et al. (2012) in the V, Rines & Geller (2008) in the r. Values in the B and g bands have been slightly shifted in λ to avoid confusion.