Saturation applies the saturation of the blending layer to the base layer while preserving the base layer’s hue and brightness. This lets you make colors more vibrant or more muted without changing their basic color or lightness.
The Math
Saturation takes the intensity of the color from the blending layer and combines it with the hue and brightness of the base layer. In other words, the top layer controls how colorful the result is, while the bottom layer controls what color it is and how light or dark it is.
Think of it like turning the color intensity knob up or down without changing the color itself or making it lighter or darker.
Core Rules of Saturation
Saturation changes: The intensity of the color comes from the blending layer.
Hue stays: The base layer keeps its original color family.
Brightness stays: The light and dark values of the base layer remain intact.
Gray removes saturation: Pure black, white, and gray have no saturation, so using them on a Saturation layer removes the color from the areas they cover.
When to Use It
Boost dull colors: Paint with a highly saturated color to make specific areas more vibrant without changing their brightness or hue.
Tone down intense colors: Use a low-saturation color to reduce overly vivid or neon-looking areas.
Targeted adjustments: Increase or reduce the vibrancy of specific parts of an illustration while preserving the existing shading and highlights.