can be computed from the chromaticity coordinates of the fixed spot of light, the variable spot of light, and the unknown, these coordinates serving to locate the respective positions in a chromaticity diagram. If the fixed light is nearly achromatic, the angle often correlates well with the hue of the color perception, and the radius fairly well with its saturation. The most fundamental way to specify the direction on a chromaticity diagram from the point representing the fixed light to the point representing the unknown light is by wavelength of the part of the spectrum required to make the match. If the unknown color can be matched by adding some part of the spectrum to the fixed light, it is said to have a spectral color, and the required wavelength is called dominant wavelength. But if a color match is produced for the fixed light by adding some part of the spectrum to the unknown color, the unknown is said to be nonspectral, and the required wavelength is called the complementary wavelength. Either dominant wavelength or complementary wavelength may be obtained for the standard observer by drawing on a chromaticity diagram a straight line through the point representing the fixed light and that representing the unknown color, and then by reading the wavelength corresponding to the point at which this line extended intersects the locus of spectrum colors. If the unknown color is plotted between the fixed light and the spectrum, the intersection gives the dominant wavelength; but if the fixed light is represented by a point intermediate to the unknown and the intersection of the straight line with the spectrum locus, the intersection indicates the complementary wave-length.
| Number | Source A | Source C | ||||
|---|---|---|---|---|---|---|
| X | Y | Z | X | Y | Z | |
| 1 | 444.0 | 487.8 | 416.4 | 424.4 | 465.9 | 414.1 |
| 2[1] | 516.9[1] | 507.7[1] | 424.9[1] | 435.5[1] | 489.4[1] | 422.2[1] |
| 3 | 544.0 | 517.3 | 429.4 | 443.9 | 500.4 | 426.3 |
| 4 | 554.2 | 524.1 | 432.9 | 452.1 | 508.7 | 429.4 |
| 5[1] | 561.4[1] | 529.8[1] | 436.0[1] | 461.2[1] | 515.1[1] | 432.0[1] |
| 6 | 567.1 | 534.8 | 438.7 | 474.0 | 520.6 | 434.3 |
| 7 | 572.0 | 539.4 | 441.3 | 531.2 | 525.4 | 436.5 |
| 8[1] | 576.3[1] | 543.7[1] | 443.7[1] | 544.3[1] | 529.8[1] | 438.6[1] |
| 9 | 580.2 | 547.8 | 446.0 | 552.4 | 533.9 | 440.6 |
| 10 | 583.9 | 551.7 | 448.3 | 558.7 | 537.7 | 442.5 |
| 11[1] | 587.2[1] | 555.4[1] | 450.5[1] | 564.1[1] | 541.4[1] | 444.4[1] |
| 12 | 590.5 | 559.1 | 452.6 | 568.9 | 544.9 | 446.3 |
| 13 | 593.5 | 562.7 | 454.7 | 573.2 | 548.4 | 448.2 |
| 14[1] | 596.5[1] | 566.3[1] | 456.8[1] | 577.3[1] | 551.8[1] | 450.1[1] |
| 15 | 599.4 | 569.8 | 458.8 | 581.3 | 555.1 | 452.1 |
| 16 | 602.3 | 573.3 | 460.8 | 585.0 | 558.5 | 454.0 |
| 17[1] | 605.2[1] | 576.9[1] | 462.9[1] | 588.7[1] | 561.9[1] | 455.9[1] |
| 18 | 608.0 | 580.5 | 464.9 | 592.4 | 565.3 | 457.9 |
| 19 | 610.9 | 584.1 | 467.0 | 596.0 | 568.9 | 459.9 |
| 20[1] | 613 8[1] | 587.9[1] | 469.2[1] | 599.6[1] | 572.5[1] | 462.0[1] |
| 21 | 616.9 | 591.8 | 471.6 | 603.3 | 576.4 | 464.1 |
| 22 | 620.0 | 595.9 | 474.1 | 607.0 | 580.5 | 466.3 |
| 23[1] | 623.3[1] | 600.1[1] | 476.8[1] | 610.9[1] | 584.8[1] | 468.7[1] |
| 24 | 626.9 | 604.7 | 479.9 | 615.0 | 589.6 | 471.4 |
| 25 | 630.8 | 609.7 | 483.4 | 619.4 | 594.8 | 474.3 |
| 26[1] | 635.3[1] | 615.2[1] | 487.5[1] | 624.2[1] | 600.8[1] | 477.7[1] |
| 27 | 640.5 | 621.5 | 492.7 | 629.8 | 607.7 | 481.8 |
| 28 | 646.9 | 629.2 | 499.3 | 636.6 | 616.1 | 487.2 |
| 29[1] | 655.9[1] | 639.7[1] | 508.4[1] | 645.9[1] | 627.3[1] | 495.2[1] |
| 30 | 673.5 | 659.0 | 526.7 | 663.0 | 647.4 | 511.2 |
| Multiplying factors | ||||||
| 30 ordinates | 0.03661 | 0.03333 | 0.01185 | 0.03268 | 0.03333 | 0.03938 |
| 10 ordinates | .10984 | .10000 | .03555 | .09804 | .10000 | .11812 |
The degree of approach of the unknown color to the spectrum color is commonly indicated by the ratio of the amount of the spectrum color to the total amount of the two-part combination; this ratio is called purity, and if the amounts are specified in luminance units, the ratio is called luminance (formerly colorimetric) purity. By far the most common convention, however, is to express the amounts in units of the excitation sum ; the resulting ratio is called excitation purity and corresponds simply to distance ratios on the chromaticity diagram of a colorimetric coordinate system [49, 64, 133]. Formulas have been derived by Hardy [49] and MacAdam [91] to
17
- ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 1.12 1.13 1.14 1.15 1.16 1.17 1.18 1.19 1.20 1.21 1.22 1.23 1.24 1.25 1.26 1.27 1.28 1.29 1.30 1.31 1.32 1.33 1.34 1.35 1.36 1.37 1.38 1.39 1.40 1.41 1.42 1.43 1.44 1.45 1.46 1.47 1.48 1.49 1.50 1.51 1.52 1.53 1.54 1.55 1.56 1.57 1.58 1.59 1.60 1.61 1.62 1.63 1.64 1.65 1.66 1.67 1.68 1.69 Values for calculation with 10 selected ordinates.
