Saturation Painting is a technique for balancing the light in images. It works by first selecting specific tones in the image. Black or white paint is then applied to a special burn/dodge layer through the selection so that the act of painting both selects the pixels that need adjustment while at the same time adjusting them either brighter or darker depending on the color of the paint. Luminosity masks are the key to making this technique work; they are the basis for the selections that are painted through. These specialized selections not only restrict the paint to the appropriate tones in the image which need adjustment, but they also feather the painting into the surrounding pixels so that the painted adjustment blends perfectly into the image.
Saturation painting takes the luminosity painting technique and applies it to saturation instead of luminosity. So in place of lightening and darkening the tones in an image, saturation painting either increases or decreases color saturation. The effect of saturation painting isn’t usually as dramatic as that achieved with luminosity painting since our eyes aren’t as sensitive to saturation changes as they are to tonal changes. However, just like luminosity painting, saturation painting can bring the appropriate saturation balance to an image and thereby improve its overall look.