Another trick using the selections generated from Channels as adjustment layer masks.

  • Load the RGB channel as a selection by cmd+clicking on it in the Channel palette.
  • Create a new Curves layer, automatically creating a layer mask with the selection.
  • Alt+click on the selection and invert it by hitting cmd+i.
  • Apply a curve to the mask by hitting cmd+m.
  • Move the leftmost point (the black point) to about a quarter of the way in. Move the rightmost point (the white point) to about three-quarters of the way in.
  • Right now, the mask is adjusted to just the midtones of the image. Return to the normal view by hitting the eye icon on the curves layer.
  • Pull up on the curve at about halfway to apply a bit of fill light to your image’s shadowy areas.