The Power of Gray - The Photoshop: Professional Retouching and Compositing Tips, Tricks, and Techniques - page 120

3. Click the thumbnail of the window in the Layers panel, and then go to Image >
Adjustments > Desaturate. Then click the layer mask attached to the window layer
( Figure 2.45 ) . With a normal medium soft-edged brush and a black foreground
color, paint around the window to hide any unwanted areas ( Figure 2.46 ) .
Figure 2.45