One way would be to create a pixel mask for a layer that's got white glyphs on a gray background. Then the background would be partially transparent while the text glyphs would be fully opaque.
Another way, which would leave the layer that defines the text "live" (editable) would be to duplicate the image and fade the background, then create a clipping mask with the full-contrast layer and the text, as shown here:
-Noel