standard illuminant

A standard illuminant in optics is a theoretical source of light with a specific, defined spectral energy distribution. These illuminants are crucial for colorimetry, the measurement of color. Different illuminants, such as daylight or incandescent lamps, have varying spectral energy distributions, which can affect how colors are perceived.123

Standard illuminants are used to ensure consistent and reproducible color measurements by providing a reference light source. For example, the CIE system defines standard illuminants that approximate conditions like daylight and light from incandescent lamps. These standards help in comparing colors accurately, as the same object can appear different under various lighting conditions.123