Turning Down the Color with the Sponge Tool in Photoshop

The Sponge tool, which soaks up color like, well, a sponge, reduces the richness (or saturation) of a color in the areas you paint. It can also perform the reverse, imbuing a specific area with richer, more vibrant colors. Surprisingly, the Sponge tool also works in grayscale mode, pushing light and dark pixels toward a middle gray, providing a darkening or lightening effect to those pixels. Unlike the Hue/Saturation or Desaturate commands (Image➪Adjustments), which work only on layers or selections, you can use the Sponge tool on any area you can paint with a brush.

You can use the Sponge tool on an image in subtle ways to reduce the saturation in selected areas for an interesting effect. For example, you may have an object that is the center of attention in your picture simply because the colors are so bright (or even garish). The Sponge tool lets you reduce the color saturation of that area (only) to allow the other sections of your image to come to the forefront. You can also use the Sponge tool to make an artistic statement: You could reduce or increase the saturation of a single person in a group shot to make that person stand out (perhaps as being more colorful than the rest).

Applying the Sponge Tool
To use the Sponge tool, just follow these steps:
1. Open an image and choose the Sponge tool from the Tools palette.
Press the O key to choose the Sponge if it is the active toning tool, or press Shift+O to cycle through the Sponge, Dodge, and Burn tools until the Sponge tool is active.
2. Select a brush from the Brushes palette.
Use large, soft brushes to saturate/desaturate a larger area. Smaller brushes are useful mostly when you need to change the saturation of a specific small object in an image.
3. Select either Desaturate (reduce color richness) or Saturate (increase color richness) from the Mode pop-up menu.
4. Choose a flow rate (the speed with which the saturation/desaturation effect builds up as you apply the brush) with the Flow slider or text box.
5. If you want an even softer effect, choose the Airbrush option.
The only special thing you need to do to use the Sponge tool in Grayscale mode is to work with a grayscale image!
6. Paint carefully over the areas you want to saturate or desaturate with color.