  We investigated the optical properties of 7 clusters of galaxies observed in
three colors over the range of absolute magnitudes -24 < M < -12. Our aim is to
estimate the Luminosity Function and the total cluster luminosity of our sample
in order to have information about the formation and the evolution of galaxies
in clusters. In this paper, we present the main points of our analysis and give
the formal parameters obtained by fitting the data using the maximum likelihood
algorithm. We find consistency between our results and other works in
literature confirming the bimodal nature of the luminosity function of cluster
galaxies. More important, we find that the relation L_opt/ L_X versus L_X is
color dependent: Low X ray Luminosity clusters have a bluer galaxy population.
