Synthetic luminosity function of hot white dwarfs obtained using different assumptions about the atmospheric composition of hot DA white dwarfs and two sets of model atmospheres, compared to the observational luminosity function of the SDSS (Krzesinski et al. 2009) – solid line and filled squares. The top two panels show the synthetic luminosity functions of hot DA white dwarfs when NLTE corrections and metal contamination, and when the corrections of Gianninas et al. (2010) to the so-called Balmer-line problem are considered. The two bottom panels display the results of our simulations when the cooling tracks of Renedo et al. (2010) are employed – that is, our fiducial model – whereas in the second bottom panel we display the results obtained when the model atmospheres of Tremblay et al. (2011) are used. In all four panels the results of the population synthesis calculations are plotted using dashed lines and open squares.