Trichromatic coefficient

Z/S, where S=X+Y+Z, are called trichromatic coefficients and have the following relation ... 

The degree of the stimulation to the red sense organ is denoted by X, to the green by Y and to the blue by Z. We call the values "tristimulus values". The value of Y is also used to denote the brilliancy of the light, because the relative luminosity curve of the pyramids coincides with the stimulus curve of the green sense organ relatively. The values x=X/S, y=Y/S and z =Z/S, where S=X+Y+Z, are called trichromatic coefficients and have the following relation ... 

Thus, a color is characterized by three numbers, X, Y, and Z, and, consequently, can be shown as a point in a three-dimensional coordinate system. Since each kind of color may be defined by its color proportion, or what is known as the standard color value proportion (trichromatic coefficient), and, by definition, the sum of all the trichromatic coefficients is unity, then, the color can be shown as a point in a two-dimensional diagram. This diagram is also known as the chromaticity diagram or color table (Figure 14-8). The line joining the points at 400 and 700 nm is called the purple line. Thus, all real colors lie within the horseshoe structure in Figure 14-8. 

Y, and Z in relation to the sum of the three designated as x, y, and z, respectively. They are sometimes referred to as the trichromatic coefficients. When written without subscripts they are assumed to have been calculated for Illuminant C and the 2° (1931) Standard Observer unless specified otherwise. If they have been obtained for other illuminants or observers, a subscript describing the observer of illuminant should be used. For example, Xio and yio are chromaticity coordinates for the 10° observer and Illuminant C. 

Trichromatic coefficients n. Alternate term for chromaticity coordinates or coefficients. See chromaticity coordinates, general, and chromaticity coordinates. 

Fig. 2. The G.I.E. Chiomaticity Diagram (rectangular co-ordinates). This diagram constitutes a transformation of Fig. 16 with rectangular co-ordinates in terms of x, y, the C.I.E. trichromatic coefficients derived from the original X Y Z trisUmulus values.

Five important treatises on color have appeared in recent years. Handbook of Colorimetry (Hardy, 1936) is a direct outcome of the eighth session of the International Commission on Illumination in 1931. It enables us to compute psychophysical values for brightness (later termed luminous refiectance and now, lightness) and chromaticity (dominant wave length and purity) from the raw spectrophotometric data. In these psychophysical terms, a colored sample may be uniquely defined with respect to its color, provided that we follow a standard procedure for determining the spectral refiectance or transmittance of the sample. The perceived color, however, is not defined, and we enter here into psychological considerations as distinct from those of psychophysics. The C.I.E. quantities x and y (the trichromatic coefficients which... 

The Gentry unit was expressly designed to correlate with the x trichromatic coefficient, and there is an almost exact inverse proportionality between it and x over the range x = 0.67 to = 0.59. (Recall that in these samples x + y = 1, so that Moster and Prater have developed a onedimensional scale on the basis of their two measurements.)... 

Trichromatic Coefficients n Alternate term for chroma-ticity coordinates or coefficients. See Chromaticity Coordinates. 

Heat test Samples will be placed for 2 h in a circulating air oven at a temperature of 175 5°F, or roughly 79 3°C. Samples should not show any significant change in either shape or general appearance when compared with the unexposed control samples. Additionally, trichromatic coefficients of the samples in the stated thickness ranges should also conform to SAE J578 standards. 

From these values, the trichromatic coefficients x, y, and z may be calculated to give an unambiguous definition of the perceived color as... 

FIGURE 7 The dependence graphics of the signal/noise function from the source altitude above the Earth surface at the random set of the natural surfaces weight coefficients (W-water surface, S-soil, F-flora) for the insects with different vision types a) monochrome, b) dichrome, c) trichromatic. 

---