Special Effects - The Photoshop: Professional Retouching and Compositing Tips, Tricks, and Techniques - page 212

Figure 4.5
7. Click the uppermost layer (light), and Option/Alt-click the layer mask icon at the
bottom of the Layers panel. This adds a black mask and hides the contents of the
light layer.
8. Press D to set the foreground and background colors to their default, and then with
a white foreground color and a normal soft-edged brush at 25% opacity, paint
around the wall light and down to the ground and pavement ( Figure 4.6 ).