Ordinarily, a mask constrains its tool’s effect to be inside all of its regions. Occasionally, it’s useful to be able to use a mask to specify an area of your photo to exclude from a tool’s effect. You can invert a mask to do this.
To invert a mask for a tool:
- Select the tool whose mask you want to invert by clicking its title bar.
- Make sure the Tool Settings tab is selected.
- Click the tool’s invert-mask box.