  We present a comparative analysis of atmospheric parameters obtained with the
so-called photometric and spectroscopic techniques. Photometric and
spectroscopic data for 1360 DA white dwarfs from the Sloan Digital Sky Survey
(SDSS) are used, as well as spectroscopic data from the Villanova White Dwarf
Catalog. We first test the calibration of the ugriz photometric system by using
model atmosphere fits to observed data. Our photometric analysis indicates that
the ugriz photometry appears well calibrated when the SDSS to AB_95 zeropoint
corrections are applied. The spectroscopic analysis of the same data set
reveals that the so-called high-log g problem can be solved by applying
published correction functions that take into account 3D hydrodynamical
effects. However, a comparison between the SDSS and the White Dwarf Catalog
spectra also suggests that the SDSS spectra still suffer from a small
calibration problem. We then compare the atmospheric parameters obtained from
both fitting techniques and show that the photometric temperatures are
systematically lower than those obtained from spectroscopic data. This
systematic offset may be linked to the hydrogen line profiles used in the model
atmospheres. We finally present the results of an analysis aimed at measuring
surface gravities using photometric data only.
