  Arguably, the best method for determining the effective temperature
($T_{\mathrm{eff}}$) and surface gravity (log $g$) of a DA white dwarf is by
fitting the Hydrogen Lyman and Balmer absorption features. However, as has been
shown for white dwarfs with $T_{\mathrm{eff}}$>50,000K, the calculated value
from the Lyman and Balmer lines are discrepant, which worsens with increasing
temperature. Many different solutions have been suggested, ranging from the
input physics used to calculate the models, to interstellar reddening. We will
focus on the former, and consider three variables. The first is the atomic data
used, namely the number of transitions included in line blanketing treatments
and the photoionization cross sections. The second is the stark broadening
treatment used to synthesise the Lyman and Balmer line profiles, namely the
calculations performed by Lemke (1997) and Tremblay & Bergeron (2009). Finally,
the third is the atmospheric content. The model grids are calculated with a
pure H composition, and a metal polluted composition using the abundances of
Preval et al. (2013). We present the preliminary results of our analysis,
whereby we have determined the $T_{\mathrm{eff}}$ for a small selection of
white dwarfs. We plan to extend our analysis by allowing metallicity to vary in
future model grids.
