Changing the transparency of a brush can help you to achieve the effects you need when using all brush based tools, including the Carbon Copy Tool, the Eraser Tool and the Dodge & Burn Tool.

Global transparency

Global transparency is controlled by adjusting the slider bar at the top of the Brushes Library, and this setting effects all brushes in the library. Increasing the transparency will make the brush stroke easier to see through when it overlays information on other layers. 0% on the slider will make the brushes completely opaque and 100% on the slider will make it totally transparent.

Individual brush transparency

The Transparency setting in the middle of the Brushes Library sets the transparency for the selected brush, and overrides the global transparency setting at the top of the library.