  We present a new technique based on multi-band near ultraviolet and optical
photometry to measure both the stellar intrinsic properties, ie luminosity and
effective temperature, and the interstellar dust extinction along the line of
sight to hundreds of stars per square arcminute. The yield is twofold. On the
one hand, the resulting reddening map has a very high spatial resolution, of
the order of a few arcseconds, and can be quite effectively used in regions
where the interstellar material is patchy, thus producing considerable
differential extinction on small angular scales. On the other hand, combining
the photometric information over a wide baseline in wavelength provides an
accurate determination of temperature and luminosity for thousands of stars. As
a test case, we present the results for the region around Supernova 1987A in
the Large Magellanic Cloud imaged with the WFPC2 on board the Hubble Space
Telescope.
