If you learn, you will talk about the color course and collocation method in detail. There are many anyway.
The definition of chromatics
Color has been used for a long time in ancient human remains, but it was not until Newton discovered that sunlight had a seven-color spectrum after passing through a prism that the science of color entered a new era. 16 ~ 17 century, there were many studies on the reflection and refraction of light, including the publication of German physicist ostwald and the appearance of Mancel in the 20th century, which led to the study of color.
There are all kinds of colors around life, including animals and plants in nature. Then what is "color"? To put it simply, light shines on an object, which makes the visual nerve feel, but color exists. さ. And the definition of color has its own definition because of different uses:
Chemist: the characteristics of dyes, pigments and other substances.
Scope of application: manufacturers and users of pigments, paints and dyes.
Physicist: A phenomenon in the field of optics.
Scope of application: optical instrument manufacturing.
Psychologist, physiologist: the consciousness that expresses the observer's consciousness.
No matter which role you play, if you want to know something about color, you must understand the three elements of color, light and color sense, three primary colors of light and color, three attributes of color, color representation, color change and color constancy.
Color consists of three elements: the observed substance, the existence of light and the feeling of the observer. Just because when there is no matter and light, if you are in a dark room, you won't feel the existence of color. If you close your eyes, I believe you won't feel the existence of color either. Therefore, to further understand the elements of color, we may wish to start with the relationship between objects and colors, light sources and colors, and observers-people and colors.
Object and color-When light is projected on an object, some or all visible light is reflected, absorbed and transmitted according to the type and structure of the object, thus showing the color of the object. The color of an object is controlled by three genes: reflection, absorption and transmission. For example, when the sun shines, it is white when it is totally reflected (disorderly reflected), black when the light is completely absorbed, and transparent when it is transmitted. Description: Reflection: When light shines on the surface of an object, part of the light is reflected. Reflection angle and incident angle are in the same viewing plane, which is called reflection, and visual experience produces texture. The reflection of all light may be opaque or specular. Absorption: If the light is partially transmitted, partially absorbed, and part of the visible spectrum light is lost, the object will appear translucent; If the light is completely absorbed, it will appear black and opaque. Transmission: When light shines on an object, except for a very small amount of reflected light, almost all the light is transparent, and the object is colorless transparent body. Scattering: When light shines on fibers containing particles or objects with rough surfaces, the reflection angle of light will change, which is called scattering.
In the existence of light source and color-color, light irradiation plays an important role. In the early stage of human evolution, people have been used to the feeling of sunlight, and it is still based on sunlight. But at night, there are artificial light sources (such as electric lamps, fluorescent lamps, mercury lamps, sodium lamps, oil lamps, gas lamps, etc.). ), because of the different spectral characteristics, it presents different colors. It leads to different colors of the same object under different light sources, which is called color development.
Due to the influence of natural light source, color, time, weather, observation direction, season and geographical location, it is very inconvenient to evaluate the color, so it is called CIE for short. 1930 has various standard light sources which are very close to natural light.
Interpretation of light-human naked eye, although due to the sensitivity difference between individuals; But the naked eye's perception of color is still a very delicate color measuring machine, and it also needs a light source. In terms of sunlight in Ethernet, there are all kinds of rays. In the electromagnetic spectrum, the wavelength of visible light wave only occupies a very narrow range. From about 380 nm to 760 nm (1 nm = 10-9m), their colors are purple from 380 nm to 430 nm, blue from 430nm ~485nm, yellow from 485nm to 570 nm, orange from 585 nm to 6 10 nm and 66544, respectively. Because everyone has different feelings about light, the wavelength of light and the brightness of sunlight-spectrum are slightly defined as the wavelength of visible light from 380 nm to 760 nm, and the brightness is different according to the wavelength. Visible light is bright in the middle region and weak at both ends. The brightness and darkness of the wavelength perceived by vision are also different. For example, yellow-green at 555nm is the brightest in bright places, and blue-green at 5 10nm is the brightest in dark places. This is called the Pukini phenomenon.
Additive color mixing and subtractive color mixing-Generally speaking, when color and light are mixed, it will produce a bright feeling because of the increase of light quantity. This mixing of color and light is called additive mixing or positive mixing. However, when dyes or pigments are mixed, the color usually darkens, which is called subtractive mixing or negative mixing. When the three primary colors are used in subtractive color mixing, if each color is absorbed properly, it will eventually become black; In the case of additive mixing, if the intensity of light is appropriate, the final light will be very white and bright.
Visual perception of human eyes-colors perceived by human eyes can usually be divided into two categories, as shown in the following table:
┌ White
Non-colored gray
│ └ Black
Color zeta
│┌ Pure color
└ Color┤
Other conventional colors
According to physics, white, gray and black can still be regarded as colors. White contains the vibration of several monochromatic lights with different wavelengths, that is, the quantitative mixing of colored lights, which is a unified complex. After physical total reflection, of course, our eyes can't detect it, so we really can't say it's color. Black is an external stimulus and can't reach the state of our eyes at all. In other words, if black is not set off by the surrounding objects, then black itself has no meaning of existence. The colors at both ends of the diameter of the color ring are complementary. A proper mixture of two complementary colors is white in terms of light and black or gray in terms of pigment.
According to Young -Helmholtz's hypothesis, there are three basic color perception optic nerves in visual perception. When light reaches the optic nerve, it stimulates the brain to feel the color, and these three spectral elements are the feelings of red, green and blue, which are collectively called the three primary colors of light.
Why is it called the three primary colors of light? Mix the three primary colors of red, green and blue to make white. In addition, red, yellow and blue visible through the reflection or transmission of other objects are mixed into black, that is, the three primary colors. In addition, the application in pigments is generally the mixture of red, yellow and blue pigments, which leads to the reduction of reflected light and the appearance of black and nearly black tones. Two of the three primary colors, red, yellow and blue, are mixed to produce green, purple and orange tones, which are secondary colors. Now it is represented by yellow (Y), red (R) and blue (B) codes, and the derivatives of its secondary colors are Y+R = O, Y+B = G and B+R = P.
The expression of color-the use of color has a long history. They used to be named after traditional names, such as gold, silver and autumn colors. With the development of society, there are more and more colors, and the traditional color expression can no longer be expressed correctly. Then with the use of color cards and color samples, color samples are easily dyed and faded. Therefore, it has more scientific, inductive and optical research and display. Slightly behind:
(1) qualitative representation-color naming method.
(2) Quantity represents-1. Sensory method (three attribute method).
2. Physical methods.
Color naming method and color representation method are usually used in automation together with color determination method. For example, the ISCC- National Bureau of Statistics method currently used in the United States was formulated by the American Committee on Color of the International Society and compiled by the American National Bureau of Standards.
This method can be easily expressed and based on natural colors. Colors can be conveyed through concepts, but there is no specific numerical relationship between them, such as black, dark, medium gray, light gray and white, or brightness or color modifiers before their hues. So it is difficult to deal with scientifically. Take Japanese industry as an example, about 500 ~ 1200 color names are used.
The method of feeling-that is, the representation of its three attributes. Comparing the color names with the naked eye according to the standard color ticket can make the color names express correctly, which is of great use in industry. Representative color systems are ostwald system, Mancel system and Japanese color research institute system. All three systems are represented by three numbers or marks. These three methods are suitable for objects with uniform surface color, such as dyed objects, painted objects and ceramic objects, but they cannot show transparent and translucent colors.
Physical color representation-193 1 year CIE (commission intuition de' l e' clairage) or ICI (international commission on illumination) formulated a physical measurement method for quantitatively representing colors with digital patterns, which is explained as follows:
Physical representation principle: the color of an object is expressed by spectral reflectivity. Color appears on the surface of the object irradiated by the white light of the sun, which gives people a special color feeling because it selectively absorbs the specific wavelength part of the white light. It belongs to the gray achromatic color series, and it is a color feeling obtained after uniformly absorbing all wavelengths in the field of vision.
The spectral reflectance curve shows that the light with various wavelengths between 400 nm and 750 nm irradiates the white surface and the colored surface, and the reflected light intensity of the white surface is 100, and other whites are expressed as a percentage relative to this. This representation is easy to understand. When dyes with known structures are dyed on specific fabrics, the color matching and concentration of dyes can be increased or decreased. However, for a specific color of spectral reflectance curve, it is limited to one color. On the contrary, for a certain color, there are infinite combinations of sufficient spectral reflectance curves. Moreover, due to the problem of color development, a standard light source must be used as the measuring light source.
(1)X, y, z notation: a method of representing numerical values through physical measurement. X, y and z are used to represent the anti-stimulus values derived from the three primary color stimuli, and then chromaticity coordinates are introduced. The tristimulus value can be calculated from the spectral reflectance curve, and its calculation methods include equal interval wavelength method and selective wavelength method, which can accurately represent the color. In addition, for example, x and y of tristimulus values can be converted to represent chromaticity coordinates on the X-Y chromaticity diagram.
(2)U*V*W*, Lab method: developed from the X-Y-Z method, which makes the color difference of two colors conform to the perceptual difference, and uses the color representation method in the chromaticity coordinate space. It is convenient to review the difference between color and standard color, which is called color difference. The color difference (△ E) is equivalent to the geometric distance between the standard color and the sample color space, and is expressed in numerical value. As for the unit of color difference, the color difference of NBS unit is generally used.
The determination methods of color are:
(1) Visual comparison method:
A side-by-side comparison method: compare the colors of samples and standards with the naked eye. At this time, we should pay attention to the material of the sample, the side-by-side direction and the lighting source.
B. Mixed isochromatic method: the sample is irradiated with a white standard light source as a benchmark, and then the three primary colors are mixed according to the addition and subtraction of the light quantity to obtain the light with the same color as the sample.
(2) photoelectric colorimetry:
A. stimulus value method.
B. Colorimetric calculation method.
Heterochromism can also be called metamerism, metamerism or metamerism. It can also be simply defined as: two-color stimulus has the same color appearance under a certain reference light source (generally referred to as simulated average sunlight →D65), but it has different color appearance (so-called color difference) under certain two light sources (such as tungsten filament illumination →A). In application, its color change is important for color-related industries (for example; Printing, textile, ink, plastics, color TV, lighting, architecture, art, etc. ) often cause great trouble in color quality management, and even suffer serious losses in improving production costs due to rejection and compensation. Therefore, the evaluation of color difference is an important part of color detection technology.
As far as color detection technology is concerned, it can be divided into qualitative method and quantitative method. Commonly used qualitative methods are:
(1) Visual inspection method: use multi-light source standard color matching lamp to observe the color or color difference changes of color sample pairs under different standard light sources.
(2) Reflectance curve method: According to the intersection of the reflectance curve (or transmittance curve for transparent objects) of the object color, judge the size of color change, that is, the more intersection points, the smaller the color change. But there are at least three intersections, that is, the greater the color difference of the color-changing pair, the intersection of its reflectivity curve will be concentrated on the three intersections. These three intersections are 450nm, 540nm and 6 10nm respectively, which are called the pressure center wavelength.
As far as quantitative methods are concerned, CIE L*a*b*, CMC and other color difference formulas are often used to calculate the color difference of color sample pairs under different light sources to evaluate the color variability of color sample pairs.
Color constancy can also be called homochromatic spectrum or color constancy. Its relative feature is the constancy of color, that is, metamerism. Color constancy and color change are two sides of the same object, so they are easy to be confused. The simple way to distinguish is that color constancy refers to a single color stimulus, while color change refers to a two-color stimulus. In other words; If a color stimulus has the same color appearance under a certain reference light source and other light sources, it is said that the color stimulus has color constancy. Everyone with normal color vision will have the same experience in daily life, that is, most natural objects have the same color appearance under different natural light, which is called color constancy. However; Due to the progress of human science and technology civilization, its artificial pigments or inks and light sources or lighting are increasing and various, which greatly improves the color constancy of objects in daily life and surrounding environment. Therefore, how to effectively manage color application has become a very important topic.