tristimulusväärtusi

Tristimulusväärtusi, often referred to as tristimulus values, are numerical representations of color. They are derived from the human eye's response to light, specifically how the three types of cone cells in the retina perceive different wavelengths of light. These values quantify the amount of stimulation each of these three cone types receives.

The tristimulus system is based on the concept that any color can be matched by mixing three primary colors. In colorimetry, these primary colors are not necessarily the same as those used in printing or display technologies. Instead, they are hypothetical reference primaries, often denoted as X, Y, and Z, which are defined such that they correspond to the spectral response of the three types of human cone cells. The X value generally relates to the sensitivity of the red cones, the Y value to the green cones, and the Z value to the blue cones.

These values are determined by integrating the spectral power distribution of a light source or an object's reflectance curve with the three color-matching functions, which represent the sensitivity of each cone type across the visible spectrum. The resulting X, Y, and Z values are then used to define a color in a way that is consistent with human perception. The Y tristimulus value is particularly important as it is closely related to the perceived luminance or brightness of a color. Tristimulus values form the basis for various color spaces, such as CIE XYZ, and are fundamental to color measurement and standardization.