desaturation

Desaturation is the reduction of color saturation—the intensity or vividness of color—in a color image or object. It is a standard term in color theory and image processing and is the opposite of saturation; complete desaturation yields grayscale, which contains luminance information without color hue.

In digital imaging, desaturation is achieved by lowering the saturation component in color models such as HSL or HSV. Partial desaturation preserves some color while reducing vibrancy; full desaturation removes nearly all color information. Artists and photographers use desaturation to influence mood, readability, or focus, for example by muting backgrounds while keeping subject colorized, or by converting an image to grayscale for a classic look. Desaturation can be performed as a global adjustment or locally with masks and selective edits. Vibrance adjustments aim to desaturate less-saturated colors more gently than standard saturation controls.

In medicine and physiology, desaturation refers to a decline in blood oxygen saturation, usually reported as SpO2. Normal values at sea level typically range from about 95% to 100%. Desaturation below about 92% is often clinically significant and may indicate hypoxemia due to respiratory or circulatory problems, high altitude, anemia, carbon monoxide exposure, or methemoglobinemia. It is monitored with pulse oximetry and, when needed, supported by supplemental oxygen or advanced therapy.

The term can also appear in other technical domains with analogous meaning—reducing the presence of a particular color, solute, or gas—though the context determines the precise interpretation.