Layer blend modes are the biggest time savers that I have found in Photoshop. Method 4 uses layer blend modes to "hide" certain areas of the image. This works best on images such as text or line work where there is a clear separation of foreground and background.
1. For this method, I want to remove the black background of the section so that I am just left with the line work and the green aerial image behind. It wouldn't make sense to use a mask or polygonal tool because it would be too labor intensive to cut it out and probably wouldn't look that great.
2. For images where you want to hide the dark areas and keep the light areas such as the line work in this example, set the layer blend mode to "Lighten".
3. In seconds, the black background disappears and only the white line work remains. In the next example, I want to do the opposite. I want to remove the white background so that I am left with the black line work.
4. For images where you want to hide the light areas and only show the dark areas, set the layer blend mode to "Multiply".