My main research interests are stellar populations, dynamics, star formation, and dust content in spiral galaxies. At present I am using deep archival HST images of nearby spirals to measure the total average extinction and the reddening through their disks, from the counts and the colors of background field galaxies found behind them; the HDF is the prime control field for this project. I have also applied the method to measure foreground Galactic extinction to the GRB970228, with excellent results.