Thanks tiox for the complete description and details, and also I should add
- The dragon is a brush provided by Hawksmont [Chinese dragon Brushes] (http://hawksmont.deviantart.com/art/Chinese-Dragons-Brushes-67684395) (DeviantArt, no attribution required) . Dragon figure and texture were merged to apply a light effect from above and below.
About the luminosity slider what I observe is the program just simulates a Black and a white “hidden” layers above the current working layer (depending if you are decreasing or increasing luminosity the opacity from 0 to 100%, starting from 0% opacity). The less luminosity you choose (starting from 0 implies 0% black and white “hidden” layers ), the more opacity for the black “hidden” layer, the more luminosity you choose, the more opacity for the white “hidden” layer.