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 is still over on the wall. Note: Having this feature on does tend to slow the brush down a bit because it’s doing a lot of math while you paint, trying to detect edges as it goes. Also, if you paint over an area and it seems to not cover the area evenly, you might turn off Auto Mask and repaint over that area. As a general rule, I leave Auto Mask turned off most of the time while I’m painting, but as soon as I get near an edge I don’t want to affect, I turn it on for just that part of the edit.