  We present an improved spectroscopic and photometric analysis of
hydrogen-line DA white dwarfs from the Sloan Digital Sky Survey Data Release 4
based on model atmospheres that include improved Stark broadening profiles with
non-ideal gas effects. We also perform a careful visual inspection of all
spectroscopic fits with high signal-to-noise ratios (S/N > 12) and present
improved atmospheric parameters (Teff and log g) for each white dwarf. Through
a comparison of spectroscopic and photometric temperatures, we report the
discovery of 35 DA+DB/DC double degenerate candidates and 2 helium-rich DA
stars. We also determine that a cutoff at S/N = 15 optimizes the size and
quality of the sample for computing the mean mass of DA white dwarfs, for which
we report a value of 0.613 Msun. In the following step, we compare our results
to previous analyses of the SDSS DR4 and find a good agreement if we account
for the shift produced by the improved Stark profiles. Finally, the properties
of DA white dwarfs in the SDSS are weighed against those of the Villanova White
Dwarf Catalog sample of Gianninas et al. We find systematically lower masses
(by about 3% on average), a difference that we trace back to the data reduction
procedure of the SDSS. We conclude that a better understanding of these
differences will be important to determine the absolute temperature scale and
mean mass of DA white dwarfs.
