Cross processing in film photography is defined as processing film in a chemical solution meant for another type of film. This yield an interesting shift in color, and sometimes give a retro look to a picture. This effect can also be done in digital photography by manipulating the curves in Photoshop. Download this fun action set to spice up your photo instantly. Tips: For a dark photo, duplicate the image and set the duplicate layer to screen, reduce the opacity if necessary, then run the action. You can also set the duplicate layer to Soft Light or Overlay to achieve a slightly different effect.