The luminosity index lambda is calculated according to de Vaucouleurs et al. (1979) , using the luminosity class lc and morphological type t codes: . lambda = (l cc + t)/10 . where lcc is the luminosity class corrected for inclination according to the relation . lcc = l c - (c . logr25) . where logr25 is the axis ratio and c is a parameter depending on the morphological type t . (c = 2.0 for t <=5 and c = 2.0 -0.9(t-5), otherwise) .