V-band luminosity function of the Virgo cluster sample (bin width: 0.5 mag, sampling step: 0.25 mag). Open symbols denote only early type galaxies, solid symbols denote datapoints which were corrected by SDSS data. The solid line indicates a linear fit performed in −18.8 ≤ M_V ≤ −13.0 mag. The Schechter function fitted in the same interval with fixed  mag is represented by the dotted curve. The vertical line at M_V = −13.0 mag represents the assumed completeness limit. The errors come from Poissonian statistics.