Principles of chromaticity

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Chromaticity is the science of studying human's color vision law, color measurement theory and technology, and it is a comprehensive science based on physical optics, visual physiology, visual psychology, psychological physics and so on, which developed in this century. (This paper focuses on the theoretical, artistic use for reference only, art workers can choose.) ）

Chroma study
Depending on the fundamentals of chromaticity and physical optics, physical optics can be thought of as objective science and irrelevant to humans. And chromaticity is a kind of subjective science, it is based on the average sense of human, so it belongs to the category of human engineering, in light of the strong measure, the physical optics with the radiation energy of the objective unit to measure, and the chromaticity of color to the human eye of the stimulation intensity to measure.
Colorimetry is a science that studies the regularity of the perception of color in human eyes. In light of the intensity of the measurement, the physical optics is measured by the objective unit of radiation energy, while chroma is measured by the intensity of the human eye. The wavelength of radiant energy is very long red light for people but no radiant energy is very small Huangguangliang, people think that the intensity of yellow light than red light.
The color reflected in people's eyes not only depends on the characteristics of the object itself, but also has a direct relationship with the spectral composition of the light source. So the color reflected in people's eyes is the comprehensive effect of the natural properties and lighting conditions of the object itself. The conclusion that we use chromaticity to evaluate is this kind of comprehensive effect.
Chromaticity is the science of studying human's color vision law, color measurement theory and technology, and it is a comprehensive science based on physical optics, visual physiology, visual psychology, psychological physics and so on, which developed in this century.
Everyone's vision is not exactly the same. In the normal visual group, there are also certain differences. The data currently cited in chromaticity for international use is the average result of data observed in many of the normally apparent party populations. In the theory of technical application, it has enough representativeness and reliable accuracy.
International Lighting Commission (CIE)
International Lighting Commission (Commission internationale Ed I ' Eclairage-cie)
An international academic research institute that focuses on the professional terminology, photometric and chromaticity of lighting. Located in Paris. As early as 1924 years ago has been engaged in the study of standard chromaticity system, 1931 according to Wright (W.d.wright) in 1928-1929 and Gilder (J. Guild) in 1931 to study the angle of the three primary colors to observe the effect, to the average, stipulates the CIE 1931 Standard Chroma Observer spectral three-stimulus value, and according to draw a partial horseshoe curve of the * chromaticity map, called "1931 Cel-rgb System chroma map", after modification is recommended for the 1931 CIE-XYZ system, for the international general chromaticity system, called "CIE standard chromaticity system", The diagram is called the CIE 1931 chromaticity chart. In 1964, the results of the study, published in 1959 by Stiles (W.s Stiles) and Birch (J.m.bruch) and Sprinskaya (N.i.speranskaya), resulted in the development of CIE1964 complementary chromaticity systems and corresponding chromaticity maps, It is widely used in various countries in the world for chromaticity calculation and chromatic aberration calculation. In 1964, a three-dimensional concept of "uniform color space" was proposed, which was revised in 1976 and formally adopted. The CIE also proposed a certain reference light source, called "CIE standard light source".
Cutaway structure of the eye
▲ Iris (Iris):
Located at the back of the room water (aqueous Humor) that forms the intraocular pressure (front of the water crystal) determines the color of the eye white children iris pigment less, blue, old pigment increased to brown black) its muscle key can control the pupil (pupil) size (about 2-8mm changes) The image is imaged on the retina with the outside light and dark.
▲ Cornea (Cornea):
Eyeball wall front, 1mm thick, for a flexible transparent tissue accounted for the eyeball wall area of 1/6, light through the cornea warp ray refraction into the eye.
▲ Water Crystal (Lens):
The posterior transparent double convex lens of the iris, the curvature of the two surfaces is different, the thickness 4mm,9mm diameter warp ray rate by ciliary muscle (ciliary Body) contraction and change.

Vision principle
The human eye can basically be seen as an opaque darkroom contained within the sclera. It has a refractive optical system consisting of a ﹑ water crystal and a vitreous body composed of cornea ﹑ anterior chamber water, which focuses the incident light on the retina behind the eyeball to form an inverted image.
The aperture on the iris is called the pupil, and the pupil size can be changed to adjust the luminous flux into the eye. At low brightness it completely opens, the diameter can reach about 8mm, while in the high brightness environment, its diameter is about 1.5mm, its effective aperture (aperture) from F/11 to f/2, focal length is about 16mm.
The retina consists of a thin layer of photosensitive cells, the cells of which are divided into two types: one is conical, the other is rod-shaped, and they are about 125 million, unevenly distributed across the retina. These two types of cells, the role of stem cells equivalent to high sensitivity ﹑ coarse particles of black and white film, it in the very dark light can also work, but can not distinguish the color, the contour of the image is not clear enough, cone cell action is equivalent to the sensitivity of poor ﹑ particles fine color film, it in the strong light to function, Can distinguish the color, get the details of the image is clearer.
The light entering the eye passes through the pupil to the water crystal convex lens, under the action of the surrounding ciliary muscle, the lens can adjust its shape appropriately, so that objects within a certain distance range (from infinity to 15cm) can be imaged on the retina respectively, and two photosensitive cells transmit the image signal through the optic nerve channel to the brain.
Water crystal is an object with uneven refractive index, the outer refractive index of 1.38, is close to 1.41, and the focal length of the water crystal can be changed by the change of its surface curvature.
As the object is different from the eye distance, the focal length of the water crystals changes accordingly, so that the object can be clearly defined on the retina, a process called focusing.
Normal eyes in the absence of natural relaxation of regulation, infinity objects just imaging in the retina, that is, the eyes of the focal point of the eye coincides with the retina, so the eyes to observe the distant objects are not easy to fatigue, so the visual instrument adjustment should make the image into an infinite distance.
When a close object is observed, the ciliary muscle around the water crystal shrinks inward, causing the radius of curvature of the crystal to become smaller, and the focal length of the eye is shortened, as the focus of the lens moves forward from the retina, so that the object at a limited distance is imaged on the retinal.
Enlarged image of optic nerve
The light entering the eye is accepted by Rod (rod) and cone (Cone) cells (see right) on the retina (retina), and generates an electronic signal that stimulates the nerve cell layer in the brain that is adept at integrating production into visual images.
The determination of the light and shade of the rod (rod) cell, on average, is about 120 million cells, which can accept 400~600nm wavelength rays without color discrimination. Cone-shaped (Cone) cells, concentrated in the central part of the retina, can accept 400~700nm wavelengths of light, with the ability to distinguish colors, but only 6 million. This also explains why people's eyes are judged by the contrast of light and shade, which is more sensitive than the color change.

Visual persistence Phenomenon
The human eye can see an object, but because the object in the light, the object reflected or transmitted light into the human eye, stimulated the optic nerve, causing a visual reaction. When the object is removed from sight and the stimulus to the human eye disappears, the shape and color of the object will not disappear immediately as the object moves away, and it can make a short stop in the human eye for a period of about 1/10 seconds. The object shape and color in the human eye this short time stay, is called the visual persistence phenomenon. Because of this kind of visual persistence phenomenon, people can enjoy the continuous picture of film and TV. The phenomenon of vision persistence is a manifestation of visual illusion.
The ability to discern the eyes
The ability of the eye to discern the details of an object is related to the structure of the retina (mainly the distribution of the photosensitive unit above it), and the different parts are also significant differences. In the center of the retina near the optical axis of a very small area (known as the macula diameter of about 1.5mm), the highest resolution ability. The two closest points to the eye can be distinguished, called the minimum resolution angle. Under daylight illumination, the minimum resolution angle of the macula is close to 1 ', tending to the edge of the retina, and the resolution ability drops sharply. So the human eye field of view is very large, the horizontal direction of the field of view is about 160 degrees, the vertical direction of about 130 degrees, but only a central view of the 6~7度 in a small area to more clearly see the details of the object.
In addition, the eye resolution ability and lighting environment has a great relationship, in the night when the lighting conditions are poor, the ability of the eyes to resolve greatly reduced, the minimum resolution angle of up to 1 degrees.
There are about 100 different colors that people can tell. This single-wavelength shade is very vivid and is known as a solid color. Most of the colors actually seen are made up of many wavelengths of light. For example, sunlight is made up of continuous spectrum from red to blue.
Color vision (the color area of the retina)
The feeling of color is the result of the effect of radiant energy on the pyramidal cells of the retina, because the distribution of pyramidal cells is different, so different regions have different ability to feel the color.
The center of the retina can distinguish various colors, transition from the central to the periphery, and gradually weaken the resolution of the color until the feeling of the color disappears.
Observing the color of the small field and the large field of view will have different results.
The eye feels the color, not only the objective stimulation, but also depends on where the eye to accept the stimulation.
(Example: When comparing two colors, the angle value of the field of view should not exceed 1.5 degrees)

Colors of vision (color identification)
Color is the subjective feeling that the external light stimulates the human visual organ. Thus, the color of the object depends not only on the object itself, but also on the light source, the color of the surrounding environment, and the visual system of the viewer.
Generally, the various colors in the visible spectrum vary depending on the intensity of the light (red or blue). This phenomenon, which varies with the intensity of light, is called the Bechude-Park effect. But in the spectral yellow (527NM) ﹑ Green (503nm) ﹑ Blue (478nm) three points do not change with the light intensity basically.
The human eye's ability to recognize color changes caused by wavelength changes (the sensitive threshold for color recognition) is different in different locations in the spectrum. The color change that the human eye can recognize is called the sensitive threshold of color recognition.
The most sensitive place is near 480nm (cyan) and 600nm (orange), the least sensitive place is 540nm (green) and both ends of the spectrum. Sensitive place as long as the wavelength changes 1nm, the human eye can feel the color change, and most to change the 1~~2nm.
Colors of vision (classification of colors)
Color can be divided into color and non-color.
Non-color refers to white ﹑ black and various shades of gray.

　　

Color refers to a variety of colors outside the black and white series.

　　

For an ideal fully reflective object, its reflectivity is 100%, called White, and for an ideal fully absorbed object, its reflectivity is zero, which is called Black.
White ﹑ black ﹑ and gray objects the reflection and absorption of the spectral bands are not selective, they are called neutral colors.
To light, the non-color black and white change is equivalent to the brightness of white light changes, that is, when the brightness of white lights is very high, the human eye will feel white, when the brightness is very low, it felt dark or gray, no light is black.
Color vision (non-color characteristics)
1) Non-color features
Can be expressed as: lightness refers to the bright feeling of the human eye to the object.
Factors of influence: intensity of radiation (size of brightness)
General brightness, we feel the brighter the object, but when the brightness changes are very small, the human eye can not distinguish between the changes in brightness, it may be explained that the degree has not changed, but not the brightness has not changed. Because brightness is a standard physical unit, and lightness is the feeling of the human eye.
People's Experience
In the same brightness situation, we may think that the high reflectivity of the dark environment (for example, white pages in a darker environment) has a higher degree of clarity than a light environment with lower reflectivity (for example, black ink in bright environments).
Color three properties (lightness)
Color has three kinds of characteristics: lightness ﹑ hue and saturation. Hue and saturation are also known as color products (chroma).
Lightness
It refers to the degree of light and shade of color. Each color in different intensity of lighting will produce light and dark differences, we know that the various colors of the object, must be in the light, to show it. This is because the color of the object depends on the absorption and reflection of the various shades of light in the object's surface. The red cloth mentioned above is because it reflects only red light, absorbing the rest of the light outside the red light. White Paper shows light because it completely reflects the entire composition of the lights that shine on its surface. If the surface of the object absorbs or absorbs all the light in the light, the object will appear gray or black. Because the energy of the same object is different from the light emitted on its surface, the reflected energy is not the same, so the object of the same color produces the difference of light and shade under the illumination of different energy rays.
The white pigment belongs to the high reflectivity material, does not have any color to mix in the white pigment, may raise own brightness. Black pigments are very low-reflectivity substances, so in the same color in various colors (except black) the more light is doped, the lower the degree of clarity.
In photography, the correct handling of the color of the brightness is very important, if only colored without the change of lightness, there is no depth sense and rhythm, that is, we often say that there is no level.
Three characteristics of color (hue)
Tone
Refers to the difference in quality between different colors, they are the visible spectrum of different wavelengths of electromagnetic waves in the visual characteristics of the unique symbol.
The most notable feature of color is hue, also known as Hue. It refers to the difference between various colors. From the surface phenomenon, for example, a bunch of parallel white light through a prism, this light by refraction and dispersed into a color of the light band, the formation of the band of Red, orange, yellow, green, green, blue, purple and other colors, is a different hue. From the point of view of physical optics, various tones are determined by the spectral composition of the light emitted into the human eye, and the hue is formed depending on the wavelength of the spectral component.
The hue of an object is determined by the spectrum of the irradiated light source and the reflection or transmission characteristics of the object itself. For example, in sunlight, blue only reflects blue light and absorbs other ingredients. If it is illuminated by red, yellow or green light, it will appear black. Red glass in the sunlight, only transmits red light, so is red.
The hue of the light source depends on the spectral composition of the radiation and the spectral energy distribution and the perception of the human eye.
Three properties of color (saturation)
Saturation level
Refers to the purity of the constituent color is the color of purity, the degree of tonal depth. It represents the proportions of the color components contained in the colors. The larger the color ratio, the higher the saturation of the color, and the lower the saturation in contrast. In essence, the degree of saturation is the color and the same luminosity has the degree of elimination of color, the more containing the color components, the more unsaturated colors. The color saturation is directly related to the surface structure of the subject and the illumination of the irradiated object. Objects of the same color, the smooth surface of the object than the surface roughness of the object of saturation, strong light than the dark under the saturation of the light is high.
The spectrum of visible light is the most saturated color. When the spectral color (i.e. monochromatic light) is mixed with white light, its color becomes lighter, or the saturation decreases. When the amount of white light added to a certain limit, in the eyes, it is no longer a color light and become white, or saturation is close to 0, white light saturation is equal to zero. The saturation of an object depends on its reflectance (or transmittance) selectivity to the spectral line, the higher the selectivity, the higher its saturation. In other words, the saturation of the object's hue is determined by the degree of selectivity of the reflected spectral radiation on the object's surface, and the reflectivity of the object to a narrower band is high, while the reflectivity of other wavelengths is very low or non-reflective, indicating high spectral selectivity and high saturation of the object.
Different colors also have different saturation levels, red saturation is the highest, green saturation is the lowest, the rest of the color saturation is moderate. In the photograph, the high saturation color can make the person produce the intense, the beautiful kind feeling, the saturation low color is easy to make the person feel the elegance contains the rich.
The color of the visual (color characteristics)
Brightness or luminance is the light effect on the human eye caused by the brightness of the degree of feeling, refers to the degree of shade of color, also known as the color scale. Brightness has two characteristics: the same object because of the light will produce a change in brightness, the same intensity of different shade, brightness difference.
Saturation refers to the sheer degree of color. The saturation of tints is lower than the concentrated color, and the saturation is also related to brightness, the brighter or darker the same hue becomes.
The base or primary color of the shade is Red (R), Green (G), Blue (B) Three colors, also known as the three primaries of light. The three primary colors are mixed with different proportions, can be a variety of shade, but the primary color can not be mixed by other colors. The color of the light is increased, so the Mihara hue is mixed into white, and the two kinds of shade mix and become white, the two colors are complementary to each other.
The physical properties of light are determined by its wavelength and energy. The wavelength determines the color of the light, and the energy determines the intensity of the light. When light maps to our eyes, different wavelengths determine the hue of the light. Wavelength of the same energy is different, it determines the color of different shades.
Hue and saturation are called chroma (chromaticity), which both describe the color category of the color light and describe the depth of the color. The color can be fully illustrated by the Chroma plus the brightness.
Glassman Color Mixing law
1) A person's vision can only distinguish between three variations of color:
Luminance ﹑ hue and saturation
2) in the process of two components, if one ingredient is continuously changing, the appearance of the mixed color changes continuously. This allows you to export:
Complementary color Law
If the two colors are blended at an appropriate rate, they can produce white or gray, which is said to be complementary to each other. If the two are mixed in other proportions, an unsaturated color similar to a larger color component is produced. Each color has a corresponding complement.
Middle Color Law
Any two non-complementary hue mixes, resulting in a middle color, whose hue depends on the two color in the tonal order of the distance.
3) The same appearance of light, regardless of their spectral composition is the same, (in the visual effect of the same light, can be composed of different spectra, this is called the same-color spectrum phenomenon) in the color mixing has the same effect. In other words, all visually identical colors are equivalent in color blending. This can then be exported:
Color substitution Law if the color a= color b, color c= color d, ("=" in the formula means visually the same), then there is a color a + color c color b= color B + Color d. (the "+" in the formula represents the additive mix) For example: if C=a+b and b=x+y then there is c=a+ (x+y).
4) The total brightness of the blending color is equal to the sum of the brightness of the various colors that make up the blend color.
The color mixing laws above are not suitable for mixing dyes or paints.
Color Matching
A method of adjusting two colors to a visually identical or equal, called a color match. The color ﹑ hue and saturation are changed by the blending method of colour addition.
Of the two matching colors, although under different conditions, two colors will always remain the same, that is, regardless of the color surrounding environment changes, or the human eye has already adapted to other color light to observe, the two colors in the field of view always match. Known as color matching constant law. Under a given light source, a pair of objects with different wavelengths can produce the same color, a phenomenon called conditional color matching, which is called the conditional matching pair.
Blending of colors
The blending of colors is called process color. The process color is divided into addition process and subtraction process color. A few color light at the same time or rapid stimulation of human visual organs, will produce different from the original color of the new color feeling, this is the method of color addition and mixing, called addition process color.
Glassman's law argues that in a blend of two ingredients, if one ingredient changes continuously, the appearance of the blending color changes continuously. According to the color substitution law, as long as the color is the same in the sense, they can replace each other, the resulting visual effect is the same, so you can use the color mixing method to produce or replace the desired color. The mixture of dyes is called subtractive mixing. The color of red, green, and blue dyes is black after blending in the same amount.
Kubelka-munk's color mixing theory holds that: when several kinds of color materials are mixed, the total absorption and scattering are the sum of the absorption and scattering of various materials. If there is no chemical effect between the various materials, the absorption coefficient and scattering coefficient of the mixture are the sum of the absorption coefficient and the scattering coefficient of the various materials. Because the absorption of the pigment causes light energy to decline, the mixing of transparent pigments follows the subtractive mixing principle.
The law of mixing color
Different colors are blended together to produce new colors, which are called process-blending methods. Process color is divided into additive process color and subtractive process color. Additive process color is the spectral composition of each color separation, color TV is the use of red, green, blue three colors added to produce a variety of different colors. The subtraction of spectral components in color printing, painting, and film is the use of subtractive process colors. They use color materials, white light on the color material, some parts of the spectrum is absorbed, while the other parts are reversed or transmitted, thus showing a certain color. When mixing pigments, each additional pigment is subtracted from the gradations to subtract more spectral components, so the pigment blending process is called subtractive blending.
The realization method of additive process color
In order to achieve the additive process color, in addition to the three different base colors, while projecting to a full reflector to produce the additive process color, you can also use some of the visual characteristics of the human eye to achieve the addition of color mixing.
1. Time Mixing method: Three different base colors are projected to a plane at a fast enough speed, because the visual inertia of the human eye can not distinguish the three base colors, but only to see their mixed colors. The time-mixing method is the basis of sequential color TV system.
2. Spatial color Mixing method: The three primary colors are projected to the adjacent three points on the same surface, as long as these points are close enough, because of the limitation of the human eye resolution, can not distinguish the three kinds of base color, and can only feel their mixed color. The Space Affair Law is the foundation of the simultaneous making of color TV.
3. Physiological blending: When two eyes are viewed in different colors at the same time, the process color effect is also produced. For example, two eyes with red, green filter glasses, when the two eyes separately viewing, can only see red or green light, when the two eyes at the same time, just yellow, this is the physiological process of color.
Color matching (turntable matching)
Use the turntable for color mixing to achieve color matching. As shown in figure (a) on the right, it is assumed that the selected three primary colors are red (R) ﹑ Green (G) ﹑ Blue (B), their respective quantities are expressed in sector area, the matching color (C) is placed in the center of the turntable, and when the turntable rotates, the,r﹑g﹑b has the effect of stimulating the human eye. Change the proportions of the r﹑g﹑b until it matches the C. The black fan (shaded part of the picture) is added to adjust the brightness of the mixed color so that it is consistent with the clarity of C. To get the best results for the match. When C is saturated, the method with figure (a) may not be matched, at which point one of the three primary colors (e.g. B) is added to the matched color C, as shown in (b).
(a) The figure can be regarded as the additive process of the time-mixing method, the use of human eye visual persistence phenomenon, in a fast enough rotation, so that the human eye can not distinguish three colors, but only to see their mixed color.
The amount of three primary colors required to match a particular color is called a three-stimulus value.

　　

Color Matching (white screen matching)
The same position of the white screen is illuminated with a Mihara shade, and the light is blended by reflection on the screen. Change the ratio of three colors, you can achieve matching. As shown in the image on the right, the matching color c is added to the other side of the screen. After matching, the visual appearance of S and f parts in the field of view is the same.
Color matching (visual proximity match)

　　

Color matching (visual proximity match)
Different color stimuli simultaneously act on the very neighboring part of the retina, and can also produce a color mixing phenomenon. This requires that the three colors on the surface to rely on close enough. Color imaging tubes are based on this principle to achieve color mixing.
In the above three color matching methods, the second white screen matching color mixing occurs in the outside world, while the other two, color mixing is achieved through the visual organs.
Summarize the previously mentioned color matching methods:
1) The mixing of colors occurs in the outside world.
2) color mixing is achieved through visual organs.
Color contrast and color adaptation
In the field of view, the interplay of different colors in adjacent areas is called a color contrast. It includes lightness contrast, tonal contrast, and contrast of color. The general color contrast is the combined result of these three comparisons. The result of the comparison is that the difference between adjacent colors is enhanced. The human eye to a certain shade to adapt, observe another object's color, can not immediately obtain an objective color impression, and with the original to adapt to the shade of the complementary elements, need to undergo a period of time to obtain an objective color perception, the process is called color adaptation process, this phenomenon is called color adaptation.
Blackbody
Any object has the ability to constantly radiate, absorb and emit electromagnetic waves. Radiated electromagnetic waves in each band is different, that is, a certain spectral distribution. This spectral distribution is related to the characteristics of the object itself and its temperature, and is therefore called thermal radiation. To study the thermal radiation laws that do not depend on physical specificity, physicists define an ideal object-the black body-as a standard object in the study of thermal radiation.
The common light sources such as the sun, fluorescent lamps, incandescent lamps and so on are called white light. However, due to the different luminous substances, spectral composition is also very large. How to distinguish the various sources of light due to the spectral composition of the difference? This blackbody is an ideal heat emitter for this physics, with a radiation source called blackbody. Its degree of radiation is only related to its temperature.
The so-called blackbody refers to the incidence of electromagnetic waves are absorbed, neither reflected nor transmitted (of course, the blackbody still outward radiation). Obviously there is no real blackbody in nature, but many of the figures are good blackbody approximations (in some bands).
The Kirchhoff Radiation Law (Kirchhoff), the energy radiated by an object in a thermal equilibrium state is not related to the physical property of the object itself, but only to the wavelength and temperature. According to Kirchhoff radiation law, at a certain temperature, the blackbody must be the most radiant ability of the object, can be called a complete radiation body.
Temperature
When compared with other light sources and blackbody radiation, it is observed that the radiation is comparable to the radiation characteristics of the blackbody temperature (i.e., their spectral composition is the same), the temperature at this time (absolute temperature) is called a light source color temperature. In practice, this is often used in the light source of the blue spectral composition and the proportion of the red spectrum The color temperature of the light source is generally high when the blue color is higher, the red component is lower.
Colour temperature: The color of the light emitted by the light source and the blackbody at a certain temperature radiate light hue at the same time, the temperature of the blackbody is called the color temperature of the light source.
Correlated color Temperature: When the spectrum of a light source is comparable to a spectral phase of a blackbody at a certain temperature, and cannot be precisely equivalent, the temperature is called the relative color temperature of the light source.
Because the temperature of the blackbody is related to color, the name color temperature is noted, the color temperature of the light source itself is different, usually the two are not the same. For example, the incandescent light source itself temperature is 2800K, but its color temperature is 2845K.
Wayne (Wien) displacement law points out: when the absolute blackbody temperature increases, the maximum emission ability to move to the short-wave direction (see figure 2.1-1), so the higher color temperature of the light source, the emitted radiant energy is more distributed in the short wavelength of green and blue light, and the lower color temperature of the light source, Its radiation can be more distributed in the long wavelength of red light. Therefore, in the standard white light, the color temperature is lower, red, color temperature is higher, bluish.
Electromagnetic spectrum
In the range of electromagnetic radiation, only the wavelength of 380nm to 780nm (1nm=10*-6mm) radiation can cause people's visual perception, which is called visible light.

　　

Spectrum of Colors
The light color wavelength λ (nm) represents the wavelength
Red 780~630 700
Orange 630~600 620
Yellow (Yellow) 600~570 580
Green 570~500 550
Green (Cyan) 500~470 500
Blue (blue) 470~420 470
Violet (Violet) 420~380 420
Standard illumination Body
1) The standard illumination body a represents the absolute temperature of approximately 2856K of the total radiant Body (blackbody) of light.
2) The standard illumination body B represents a relative color temperature of about 4874K of direct sunlight, its light color equivalent to noon sunlight.
3) The standard illumination body C represents the relative color temperature of about 6774K average daylight, its light color approximate cloudy sky of daylight.
4) Standard illumination body D65 represents daylight with a relative color temperature of approximately 6504K.
5) Other D illumination bodies represent other daylight other than the standard illumination body D65, such as d55﹑d75. D55 represents a typical daylight with a color temperature of 5503K, commonly used in photography. The D75 represents a typical daylight with a color temperature of 7504K and is used for fine color discrimination in high-temperature light sources.
The illumination body,b and C are not ideal, so the illumination body D is used to represent daylight. In the application, a and D65 are recommended as standard lighting bodies for general application.
Standard light source
To more accurately and standardize the tone, the CIE (International Lighting Commission) has developed 4 standard light sources to unify tonal values. The names of these 4 standard light sources are shown in the table below, in these 4 kinds of standard light source, commonly used C light source and D65 light source, our country uses D65 as standard light source.
1) standard light source a temperature 2856K of gas-filled tungsten filament.
2) Standard light source B a light source plus a specific set of Davis-Gibson Liquid Filter to produce the relevant color temperature 4874K radiation.
3) Standard light source c a light source plus another set of specific Davis-Gibson liquid filters to produce the relevant color temperature 6774K radiation.
Standard illumination body D,cie has not yet recommended the corresponding standard light source.
Our country takes D65 as standard light source.
On the theory of color vision
There are two main types of modern color vision theory: One is Yang-Helmholz's three-color theory, the other is Herring's "opposing" color theory. The former from the physical law of color mixing, the latter from the inspection phenomenon, both can explain a large number of phenomena, but each has shortcomings. For example: The three-color theory is the greatest advantage is to fully explain the various colors of the mixed phenomenon, but the biggest difficulty is not satisfied with the interpretation of color blindness phenomenon. The antithesis theory can be satisfactorily explained to the phenomenon of color blindness, but the biggest difficulty is that the phenomenon of the three primaries can produce all colors is not fully explained, and this physical phenomenon is the basis of modern chromaticity, has effectively guided the development of television technology, the development of color TV technology, The color TV technology relies on the tri-color theory as the theoretical basis.
After 1971 years, the theory is gradually replaced by the belief that there are three colors of receivers that, when stimulated by light, transmit electrical signals from different wavelengths to the brain through nerve cells. And the brain will send in the signal according to the principle of opposing color theory to deal with the color of your perception. That is to say, the color receiving end of the retina of the eye reacts to the wavelength of the primary color (r.g.b) and produces a nerve electron signal sent to the brain for interpretation. The brain converts the resulting signals into red, green, yellow, and Blue (C.M.Y.K) and combines them into images.
(Source: Kirin Domain)

(turn) chromaticity principle