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1. Relative power (P) of the source of light (column 2, Table 2.2) is multiplied by each color matching function (x, y, and z) (columns 3 to 5, Table 2.2), wavelength by wavelength, to obtain the weighing factors (Px, Py, and Pz) (columns 6 to 8, Table 2.2). Values are calculated at each visible wavelength value and consequently one curve is obtained for each weighing factor (Figure 2.10A).

2. The values obtained for each curve (Px, Py, and Pz) (columns 6 to 8, Table 2.2) are multiplied by each reflectance value of the evaluated object (column 9, Table 2.2), wavelength by wavelength, to obtain the values PRx, PRy, and PRz (columns 10 to 12, Table 2.2). These values are the specific visual responses. Values are calculated at each visible specific value and consequently three curves are obtained, one for each product (Figure 2.10B).

3. As discussed above, visual color evaluation is an additive (integrative) mechanism by which the responses at each specific wavelength are considered. Consequently, areas under the curve are calculated for each of the curves obtained in step 2. Each area represents one of the tristimulus values (X, Y, and Z) of the evaluated object (Figure 2.10C). CIE has introduced mathematical models to derive the numbers associated with each color:

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