The Perfect Brush option incorporates a color-based, self-masking technology to help create precise selections and masks. When you turn the Perfect Brush option on—by clicking on the Perfect Brush icon in the Tool Options bar—the Brush collects the colors under the center of the brush and applies the effect only to those colors. This protects the adjustment from being applied across edges, such as tree branches. Further settings for the Perfect Brush can be found by clicking on the gear icon in the Tool Options bar.