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A spectral color is a color that is evoked by a single wavelength of light in the visible spectrum, or by a relatively narrow band of wavelengths. Every wavelength of light is perceived as a spectral color, in a continuous spectrum; the colors of sufficiently close wavelengths are indistinguishable.
The spectrum is often divided up into named colors, though any division is somewhat arbitrary: the spectrum is continuous. Traditional colors include: red, orange, yellow, green, blue, and violet.
The division used by Isaac Newton, in his color wheel, was Red, Orange, Yellow, Green, Blue, Indigo and Violet; a mnemonic for this order is Roy G. Biv. In modern divisions of the spectrum, indigo is often omitted; see indigo #Classification as a spectral color for details.
In HSL and HSV color models a spectral color has the maximal saturation among all colors of the same hue.
Non-spectral colors
Among some of the colors that are not spectral colors are:
- Grayscale (achromatic) colors, such as white, gray, and black
- Any color obtained by mixing a gray-scale color and yet another color (either spectral one or not spectral), such as pink, which is a mixture of a reddish color and white.
- Purple colors, which in color theory also include magenta colors, rose colors, and other colors on the line of purples, which are various mixtures of violet and red light.
- Any CMYK color.
Table of spectral or near-spectral colors
Most of colors listed do not reach the maximal (spectral) colorfulness, or are not usually seen with it, but they can be saturated enough to be perceived closely to their dominant wavelength spectral colors. Ranges of wavelengths and frequencies are only approximate. The only RGB-implemented colors which might be really spectral are its primaries: red, green, and blue.
| Color term | Sample | Wavelength, nm | Frequency, THz | Hue | Comments | |
|---|---|---|---|---|---|---|
| Red | 740–630 | 405–480 | A traditional, broad color term, which includes some nearby non-spectral hues | |||
| • red (RGB) | ? | ? | 0° | |||
| Orange Amber |
620–585 | 483–512 | ≈ 30° | |||
| Yellow | 585–560 | 512–540 | A traditional color term | |||
| • yellow (NCS) | ? | ? | 50° | Munsell yellow and gold have almost identical chroma at h = 51° | ||
| • process (canary) yellow | ? | ? | 56° | |||
| • yellow (RGB) | ? | ? | 60° | |||
| • Chartreuse yellow | ? | ? | 68° | |||
| Lime | ≈ 564 | ? | ≈ 75° | May be classified as either green or yellow | ||
| Green | 560–??? | 540–??? | A traditional, broad color term | |||
| • Chartreuse green | ? | ? | 90° | |||
| • Bright green | ≈ 556 | ? | 96° | |||
| • Harlequin | ≈ 552 | ? | 105° | |||
| • green (RGB) | ? | ? | 120° | |||
| • green (NCS) | ? | ? | 160° | Munsell green at h = 163° is nearby | ||
| Cyan | 505–480 | 593–624 | Sometimes included (or overlaps) with blue, terminological distinction between the two is inconsistent | |||
| • Turquoise Blue | ? | ? | ≈ 175° | Most of "turquoise" lies far away of the spectrum | ||
| • cyan (RGB) | ? | ? | 180° | |||
| • Blue of Munsell | ? | ? | 190° | |||
| • process cyan | ? | ? | 193° | |||
| Blue | 490–450 | 610–670 | A traditional, broad color term, which used to include cyan | |||
| • Azure | ≈ 488 | ≈ 614 | ≈ 210° | |||
| • blue (RGB) | ≈ 445 | ≈ 674 | 240° | |||
| Indigo | definition is controversial | |||||
| Violet | 450–400 | 670–750 | ? | As spectral, is very dim and rarely seen. The term also extends to purples | ||
See also
References
- Thomas J. Bruno, Paris D. N. Svoronos. CRC Handbook of Fundamental Spectroscopic Correlation Charts. CRC Press, 2005.
[http://hyperphysics.phy-astr.gsu.edu/hbase/vision/specol.html#c1 Color - http://encycolorpedia.com/007fff