5. Using the "Fill" tool (F), fill the new layer with the colour black, select its layer mask and invert (Ctrl+I).
6. Change the current layer's blending mode to "Overlay" and the middle layer's blending mode to "Difference".
7. Adjust
the opacity of the top layer to increase or decrease the brightness.
Rollover the image in this step to see the original image before this
technique was applied.