Special Effects - The Photoshop: Professional Retouching and Compositing Tips, Tricks, and Techniques - page 210

Figure 4.3
4. Click the original background layer at the bottom of the layer stack, and create a
copy by pressing Command/Ctrl+J. Rename it light , drag it to the top of the layer
stack, and go Filter > Convert for Smart Filters ( Figure 4.4 ).