  A sample of white dwarfs is selected from SDSS DR3 imaging data using their
reduced proper motions, based on improved proper motions from SDSS plus USNO-B
combined data. Numerous SDSS and followup spectra (Kilic et al. 2005) are used
to quantify completeness and contamination of the sample; kinematic models are
used to understand and correct for velocity-dependent selection biases. A
luminosity function is constructed covering the range 7 < M_bol < 16, and its
sensitivity to various assumptions and selection limits is discussed. The white
dwarf luminosity function based on 6000 stars is remarkably smooth, and rises
nearly monotonically to M_bol = 15.3. It then drops abruptly, although the
small number of low-luminosity stars in the sample and their unknown
atmospheric composition prevent quantitative conclusions about this decline.
Stars are identified that may have high tangential velocities, and a
preliminary luminosity function is constructed for them.
