Saturation masks can be a useful addition to the Photoshop toolkit. The Vibrance adjustment panel in Photoshop CS4/CS5 can make global adjustments to saturated colors and unsaturated colors (vibrance), but targeting saturation adjustments to specific colors and specific levels of saturation can be a bit more challenging. Saturation masks can help do this. I recently added a tutorial that describes one method to paint saturation and vibrance into specific parts of an image and to target either saturated or unsaturated colors when doing so. In some ways it resembles luminosity painting, but instead of changing the brightness of specific tones, saturation painting adjusts color saturation, either increasing it or decreasing it. The image below is one that included the saturation painting technique. If you roll your mouse over the image you’ll see how it looks with the saturation painting layer turned off.
The saturation painting effect is subtle but important in bringing better saturation balance to the image. The most obvious change is the increased saturation in the yellow-orange trapezoid at the top right. This area was more heavily painted to make a more dramatic saturation change. Lesser changes can also be seen however. On the left side of the image, saturation was decreased, but just slightly to take the edge off the over-saturated colors in this area. Also, on the right and moving towards the center, saturation was again increased, but not nearly as much as in the trapezoid. These last two changes, being more subtle, required less paint to achieve the desired results. That’s one of the advantages of saturation painting–the degree of saturation change can easily be altered simply by changing the amount of paint that’s applied.
These saturation changes were accomplished using the brush tool on a single layer in Photoshop. Below is what this layer looks like.
The tutorial that describes this technique is located here.