Luminosity function of LBG galaxies at z ~ 7 computed with the Stepwise method and assuming a log-normal size distribution with parameters Rh_mode = 0.09 ± 0.01 arcsec and σ_Rh = 0.06 ± 0.04. The filled symbols show the data points presented in Grazian et al. (2011) (black dots and upper limits by Ouchi et al. 2009; red squares by Castellano et al. 2010b, and cyan dots by Bouwens et al. 2010b), while the open points are the number densities for the HUDF (triangles) and P12HUDF (circles). The cosmic variance between the two fields is greater than the statistical uncertainties.