How Do I Do That in Photoshop?

Keep from Painting Outside the Lines?

Turn on the Auto Mask checkbox (near the bottom of the Adjustment Brush panel)—this helps to keep you from accidentally having your brush spill over onto areas you didn’t want affected by it. With this turned on, only the area under the little plus-sign crosshair in the center of the brush will be affected (see the image above where I’m painting on the wall to the left of the stairs, and even though my brush is clearly extending over onto the stairs, it doesn’t brighten the stairs at all because the crosshair ...