While painting red and gray on the saturation painting layer is an easy way to affect saturation in specific parts of the image, it has a potentially serious drawback—it affects all colors that are painted regardless of their degree of saturation. An image normally has significant saturation variation in its colors. If red is painted in an area to boost the saturation of under-saturated colors but accidentally strays over some already too-saturated colors, the too-saturated colors will get even more saturated as a result. Likewise, accidentally painting gray over already under-saturated colors will also decrease their saturation. In order to saturation paint effectively, it's necessary to restrict where the paint lands on the saturation-painting layer, and this is where the Saturation and Vibrance masks come into play.
Painting through a Saturation mask selection insures that pixels with the most saturated colors receive paint. Painting through a Vibrance mask selection directs the paint to less saturated colors. So by first loading the appropriate mask as a selection and then painting through it with the appropriate color paint, accidently changing the color saturation of any area, or even any pixel, is significantly reduced. The mask selection makes sure that the correct pixels get paint and prevents other pixels from being painted. And, because the Saturation and Vibrance masks are created using the saturation values of the pixels themselves, most pixels are only partially selected depending on their degree of saturation. This ability to partially select pixels makes sure that the paint strokes on the saturation-painting layer blend naturally with the surrounding areas.
There are generally just two desired outcomes with saturation painting—increased or decreased saturation. The following table describes them and the paint and mask to use for the best outcomes with saturation painting.
| Desired outcome: | Decrease saturation of over-saturated colors | Increase saturation of under-saturated colors |
| Mask to paint through: | Saturation mask | Vibrance mask |
| Color to paint with: | Gray | Red |
Looking closer at the image shown in the Introduction will show how this occurs and provide a clearer understanding of how saturation painting works.
| Introduction |
| PREVIOUS—Special Layer/Special |
| YOU ARE HERE—Incorporating the Masks |
| NEXT—Saturation Painting Example |
| Summary |