I had a customer send me a .png, black on a transparent background, RGB mode, it has some soft edges. Normally, I'd open Levels or Curves, and bring the ends together to "harden" it and lose the grays. No matter what I do, absolutely nothing happens to the image. If I take the eyedropper tool, and have the Info pallet open, when I hover over black, I get "0" in the RGB section, and like 60,60,60, 80 in the CMYK section. Also, there is no Histogram in the Curves box, or the Levels box. Hmmmm...
Steve