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Of The Colours

TBR
Posts: 9,991
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3/27/2016 7:00:41 PM
Posted: 8 months ago
At 3/27/2016 6:09:33 PM, UUU wrote:
How many primary colours exist and what puts a limit to their number?

Well... Three. The point is, they are colors that can not be made by combining other colors, so the limit is, what colors can not be created by combing other colors.
chui
Posts: 507
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3/27/2016 7:57:56 PM
Posted: 8 months ago
At 3/27/2016 6:09:33 PM, UUU wrote:
How many primary colours exist and what puts a limit to their number?

The retina of a human eye has three types of colour receptors: red ,blue and green.
Mhykiel
Posts: 5,987
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3/27/2016 10:43:25 PM
Posted: 8 months ago
At 3/27/2016 6:09:33 PM, UUU wrote:
How many primary colours exist and what puts a limit to their number?

Consider the only colors we can detect, are those that are in the color space of the receptors of the eye.

Considering this domain, there are three colors for light. And 3 colors for pigments.

IN addition to hue, we detect luminosity, and opaqueness. When it comes to pigment White can not be created by mixing Red, Blue, or Yellow. However All colors light enough appear white. So white and black are technically classified as shades or tints.

Red Blue Yellow for pigments

Red Green Blue for Lighting.
RuvDraba
Posts: 6,033
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3/29/2016 10:20:44 PM
Posted: 8 months ago
At 3/27/2016 6:09:33 PM, UUU wrote:
How many primary colours exist and what puts a limit to their number?

Light falls in a wide spectrum, U^3, but human eyes perceive only a segment of that spectrum (around 400-700nm wavelength or 430-770THz frequency.) Our eyes do this through photochemical reactions [http://www.livescience.com...], and the pigments used are responsive more to some frequencies than others. Since human eyes are normally trichromatic (i.e. containing three light-sensitive pigments, though some women have four [https://en.wikipedia.org...]), we can access all the visible colours available to the human eye by adding combinations of three distinct frequencies to darkness, one from the spectral range of each pigment. You can also subtract frequencies from 'white' light for a similar effect.

Within the spectral range of each pigment, you can pick almost any frequency to add or subtract, however each pigment has a spectral sensitivity curve, which works like a frequency-response function in an audio speaker. [https://en.wikipedia.org...] If you add frequencies close to the maximum spectral sensitivity for each pigment, you tend to get a bigger range of results, and if you subtract frequencies between the spectral sensitivities, it's the same.

Thus, in additive applications like TV, projection and theatrical lighting, red green and blue work well, while in subtractive applications like printing, cyan, magenta, yellow and black work well. However, earlier, red, yellow and blue were standard for painting, and some early colour techniques even used orange, green and violet. [https://en.wikipedia.org...]

So although the same primary colours are shared by almost all humans and might seem part of the order of nature, they're actually a subjective effect of human neurobiology. Essentially, how much colour you can produce depends on what you know about the eye, and what additive light frequencies and/or subtractive pigments you can engineer.

I hope that may be useful.