  As the first step to determine disk mass-to-light ratios for normal spiral
galaxies, we present the results of an imaging survey for planetary nebulae
(PNe) in six nearby, face-on systems: IC 342, M74 (NGC 628), M83 (NGC 5236),
M94 (NGC 4736), NGC 5068, and NGC 6946. Using Blanco/Mosaic II and WIYN/OPTIC,
we identify 165, 153, 241, 150, 19, and 71 PN candidates, respectively, and use
the Planetary Nebula Luminosity Function (PNLF) to obtain distances. For M74
and NGC 5068, our distances of 8.6 +/- 0.3 Mpc and 5.4 +0.2/-0.4 Mpc are the
first reliable estimates to these objects; for IC 342 (3.5 +/- 0.3 Mpc), M83
(4.8 +/- 0.1 Mpc), M94 (4.4 +0.1/-0.2 Mpc), and NGC 6946 (6.1 +/- 0.6 Mpc) our
values agree well with those in the literature. In the larger systems, we find
no evidence for any systematic change in the PNLF with galactic position,
though we do see minor field-to-field variations in the luminosity function. In
most cases, these changes do not affect the measurement of distance, but in one
case the fluctuations result in a ~0.2 mag shift in the location of the PNLF
cutoff. We discuss the possible causes of these small-scale changes, including
internal extinction in the host galaxies and age/metallicity changes in the
underlying stellar population.
