The C.I.E Primaries

The Commission Internationale d'Eclairage derived a new set of primaries using the blue, green, and red primaries in both positive and negative combinations. This new set of primaries, called X, Y, and Z, have the following properties:

1. They always produce positive tristimulus values.
   它们总是产生正的三刺激值。
2. It is possible to represent any color in terms of these primaries.
   任何颜色都可以用这些基色来表示
3. They were derived so that equal values of X, Y, and Z produce white.
   它们被推导出来，使得X、Y和Z相等时产生白色。
4. They were arranged so that a single parameter Y determines the luminance of the color.
   它们被安排成由单一参数Y决定颜色的光亮度。
5. They are related to the sensitivity of the human eye by the use of color matching functions which match to the C.I.E. 1931 Standard Observer.
   它们通过使用与C.I.E. 1931标准观察者匹配的颜色匹配函数，与人眼的灵敏度相关。

The C.I.E. Color Matching Functions

If the spectral power distribution (SPD) for a colored object is weighted by these curves, the CIE chromaticity coordinates can be calculated. 如果彩色物体的光谱功率分布（SPD）乘以这些曲线加权，就可以计算出CIE色度坐标。

Additive Color Mixing with CIE

The result of adding two colors of light can be worked out as a weighted average of the CIE chromaticity coordinates for the two colors. The weighting factors involve the brightness parameters Y. If the coordinates of the two colors are

then the additive mixture color coordinates are

This linear procedure is valid only if the colors are relatively close to each other in value.