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Latest date : 03/06/2013

CIE1931 Standard Colorimetric System (XYZ)
CIE (1976) L*u*v* Color Space
---Difference limen range in u'v' chromaticity diagram
CIE (1976) L*a*b* Color Space
Munsell Color System
PCCS [ Practical Color Co-ordinate System ]
Ostwald System
NCS-Natural Color System
ABC Tone System --- Handicraft of the Color Solid
7 Colors Printing System Designer's Color Atlas [ DCA ]

* Illustrations contained in this Color System were featured in the 1993-2002 Art Calendars of Dainichiseika Color & Chemicals Mfg. Co., Ltd. to disseminate the teachings of colors to the public. Any reproduction is strictly prohibited.



CIE1931 Standard Colorimetric System (XYZ)
A system commonly employed in expressing colors is called Colorimetric System and the CIE 1931 Standard Colorimetric System introduced here is the basic format of color expression. The CIE 1931 Standard Colorimetric System was established at the 1931 conference of Commision Internationale de Iユツlairage (CIE) as a means for precisely defining the color of light. Based on the principles of the trichromatic system, the light for each color, formed by combinations of the three primary colors (red, green and blue violet), is assigned a numeric value.
Monochromatic spectra are lined up on the perimeter of the curved spectrum locus in the x, y chromaticity diagram as shown. The linear section is called the purple boundary. Moving toward the central section, you get the intermediate colors and at the center itself you get white illuminant. All the colors of light are contained in this diagram and each one can be defined using the x, y values together with light intensity.
Although the use of a such a diagram showing the colors of light is not an accurate method for color printing purposes, we thought it would make our subject more comprehensible to the general reader.


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CIE (1976) L*u*v* Color Space
Difference limen range in u*v* chromaticity diagram
L*u*v* color system and L*a*b* color system are both uniform color spaces that were adopted in 1976 by Commission Internationale de lユツlairage (CIE) and are also referred to as the CIE LUV color space.
The diagram consisting of u'v' coordinates, the chromaticity values of the above color system, is called the u'v' chromaticity diagram and is also referred to as the CIE 1976 UCS (Uniform Chromaticity Scale) diagram.
Uniform color space refers to a color space with a sensuously uniform scale property, a color space in which the sensuous differences of uniform luminance colors in all areas of the chromaticity diagram lie in more or less geometric distances.
The XYZ color system, the basic color system, was adopted by CIE in 1931 but this system does not have the properties of a uniform color space.
In 1942, MacAdam announced the drawing of an ellipse that is interrelated to the human difference limen on the xy chromaticity diagram by referring to the disparities seen in the color matching experiment that uses monochromatic light.
It is the so-called MacAdam ellipse. According to this ellipse, between the ellipse of the purple domain and that of the green domain, there is a ten-fold difference between the longest and shortest diameters. Thus, in the purple domain, just a tiny color difference makes the colors look different while the same does not apply to the green domain.
To further clarify these results, MacAdam has enlarged the size of the ellipse ten-fold, but in the ideal uniform color space, the ellipse must be a circle and the size must be uniform.
The L*u*v* color system is the XYZ color system with converted coordinates; it is a diagram in which the MacAdamユs ellipse and the 4 points where the long diameter and short diameter intersect have been converted to u'v' values, transferred to the u'v' chromaticity diagram and linked by an arc on a geometric plane.
If we compare it with MacAdamユs ellipse on the xy color chromaticity diagram, there is little disparity in size and we can estimate that it is now closer to the uniform color space.
That is why the L*u*v* color system or L*a*b* color system is being used as the color system to calculate the color difference instead of the XYZ color system that
is not suitable for expressing the color difference.

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CIE (1976) L*a*b* Color Space

The L*a*b* color system is based on a uniform color space CIE LAB (L*a*b* color space). In a uniform color space the distanse between two points (two colors) is nearly proportional to the perceptual color difference. The L*a*b* system is recommended by CIE (Commission Internationale de lユツlairage) not only for specifying objects-colors but also for calculating color difference.
The L*a*b* color system is often used in Japanese industry as a standard color system in the field of color management, as well as color reproduction, such as color photograph, color facsimile, color print, color copy, etc.
In order to assist in further understanding of colors in process printing, the color reproduction range produced by the three primary colors, yellow (Y), magenta (M), and cyan (C), is represented in the L*a*b* color space.
The positions of colors produced by printed layers the three primary colors are plotted in the ground plan a*b* which gives a birdユs eye view.


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Munsell Color System
In terms of the basics of color system i.e., we are exhibiting the representative color system for describing the color of objects.
The diagram shown here is used as a scale for object color. It displayes the color solids of the Munsell Color System, the one most commonly used in Japan and the United States.
The Munsell Color System, first published in 1905, was created by Albert H. Munsell (1858-1918) an American painter and art teacher.
Munsell described the system he created in his "Atlas of the Munsell Color System".
A later work, the "Munsell Book of Color" based on his Atlas, was first issued in 1929. In 1943, the Colorimetry Committee of The Optical Society of America scientifically revised Munsell's work, reissuing it as the Munsell Renotation System. It is this revised version which is commonly known today at the Munsell Color System.
In Japan, the Munsell Color System has been adopted as JIS Standard Color System for object-color.
In the Munsell Color System, a single color is represented by three separate parameters (three dimensions) of color: hue(H), value(V) and chroma(C).
 

Hue expresses the basic quality of the color; there are a total of ten hues consisting of the five basic hues "red(R), yellow(Y), green(G), blue(B) and purple(P)" and five intermediate hues :"yellow red(YR), green yellow(GY), blue green(BG) , purple blue(PB) and red purple(RP)." These form a hue cicle arranged in sequence on the circumference. For each hue, there is a number from 0 to 10 placed before the symbol for the hue. It denotes value, the measure of lightness. The lightest white is given a 10 and placed at the top, while black is given a 0 and placed at the very bottom. Between these two extremes, shades of gray are arranged in perceptible equal steps. Chroma is the measure of the saturation of color. The central axis of achromatic color is defined as 0 and the scale is arranged concentrically. The farther one moves away from the center, the greater the saturation of the color. The three dimensions of color - hue, value and chroma - indicated also by numbers to the right of the decimal point, are utilized as an accurate yardstick for representing object-color. The steps employed are set up so that the degree of differentiation between each step is perceived as equal. A value differential of 1 and a chroma differential of 2 are set up such that they are perceived visually as having the same degree of difference.
In this diagram, hue is placed on a scale of 40 marked off at intervals of 2.5, value is placed on a scale of 10 marked off at intervals of 1 and chroma is marked off at intervals of 2. With respect to chroma, the ceiling value for color saturation will vary with each hue.
Although printed reproduction does not allow for an absolutely accurate color rendering, it should give you a good idea of the concept of the Munsell Color System and the shape of the color spaces.The indication for a single color is expressed by hue, value and chroma, in that order. For instance, we use an indication like 5R4/14 to accurately transfer data about color.

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PCCS [ Practical Color Co-ordinate System ]
PCCS is a color system made public in 1964 by Japan Color Research Institute, who developed it as a color system to put in practice its new color co-ordinate theory, derived from over 10 years of study and research on color harmony.
It has greatly contributed to the education and practice of color harmony in beaux-arts and designing, and is recognized as a color system of Japanese origin.
This system is composed of three separate parameters of color perception, namely, hue, value and chroma, and is characterized by its capacity to be used functionally as a hue/tone, two-dimensional system.
Both the Munsell Color System and the NCS are difficult to indicate because colors are represented three-dimensionally, adding further complexity to the study of colors. In the case of PCCS, it has the advantage of enabling the user to intuitively understand the representation of color. Tone is a compound concept of value and chroma, and indicates the メtone of colorモ such as bright or dark, strong or weak. By representing the tone of colors through the use of adjectives, systematic naming of colors is facilitated, thereby enabling the user to familiarize more easily.

As indicated in the diagram, tones are separated into 12 chromatic colors and 3 achromatic colors, which are codified.
The hues in the PCCS are basically made of 8 colors including psychological four primary colors, red, yellow, green and blue, and their four complimentary colors (afterimages) plus four in-between colors with the same degree of difference.
Between these 12 colors, further colors are added to compose a hue circle of a total of 24 colors. In this hue circle, the three optical primary colors and colors close to the three primary colors of color materials are included. The number 24 is a measure of 2 and 3, convenient for the arrangement of colors.
The Munsell value system is used to indicate value in the PCCS, with a 0.5 scale indicator, indicating 9.5, 9.0, 8.5.... Chroma in the PCCS introduces the concept of saturation, adopting chroma of 11 levels, with the maximum set at chroma 10s as a virtual pure color common to all hues. This is a distinct feature not found in the Munsell color system.
Color in the PCCS is represented by combining the hue number from 1 to 24 and the tone in abbreviated letters, v2 (vivid red), dk16 (dark greenish blue) are examples of the two-characteristic (hue/tone) representation. In the world of color coordination, it is important that the combination of coloring is kept simple and can easily convey the image.
While the Munsell Color System possesses an analogue continuity, PCCS is digital, which fact makes this representation system not only distinct, but also a more modern system suitable to the present age.

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Ostwald System
Ostwald System was developed by the German scientist Wilhelm Ostwald (1853-1932) who is regarded as one of the fathers of modern physical chemistry. Introduced in 1923, Ostwald System succeeded in further systematizing both psychologically and physically the study of color.
According to Ostwald System, the color of an object is made up of pure color along with white and black. Then, with respect to red, yellow, green and blue, an imaginary full color is assumed. The four colors; red, yellow, sea green and blue form two complementary sets. (This arrangement is such that mixing of the complementary sets yields achromatic color.)

Psychologically, these four colors function as primary colors. These four colors are arranged into four equal sections on a circle, each of which is further divided into two equal sections thereby increasing the number of colors to eight. Spaces between each color are then divided into three equal parts to yield a hue circle with a total of 24 hues (hues 1-24). The equilateral triangle formed by connecting points from the pure color, black and white categories is known as a monochromatic triangle. The space surrounded by 24 equilateral triangles mainly along the black and white axes is known as the Ostwald color solid.
In this color system, at intervals along the white to black scale, fifteen achromatic colors with white and black content are arranged. These are labeled as 'a' through 'p'(with 'j' excluded). In the interval corresponding to pure color, 'pa' and either 'a' or 'p', an additional fifteen achromatic colors are also arranged. Finally, at the intersecting points of each monochromatic triangle 105 chromatic colors are arranged. As a scale which applies the logarithms's law of Weber・echner, the perceptual content and physical stimulus values on the achromatic color scale in Ostwald System vary logarithmically in relation to each other. The same is true of white and black content in the chromatic color section. Moreover, additive mixture of white content, black content and full color content is accomplished by rotor rotation (additive mixture of color stimulus). Ostwald color solid and the color inside the monochromatic triangle share either equivalent dominant wavelengths or complementary wavelengths. Colors with the same color code number have equivalent white, black and full color content.
This extremely high level of orderliness is one of the outstanding features of Ostwald System.
In terms of color design, Ostwald System offers the convenience of producing mechanical color harmony. To this end, the Container Corporation of America has published the Color Harmony Manual which establishes a color standard composed of sets of one hue 28 colors. The Manual is widely used in the design field.
The color solid discussed above is shown in simplified form.


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NCS-Natural Color System
"Natural Color System"(NCS) was presented by Sweden Color Center at the occasion of the First AIC (Association Internationale de la Couleur) Congress, held in Stockholm in June of 1969. The outline of this presentation is introduced in the first issue of the organ of Color Planning Center, "Color Communication," of October of the same year (written by MINATO Sachie).
NCS is a standardized abstract system which expresses perception, and is based on psychological primary colors in accordance with E. Heringユs opponent-color theory. Therefore, in that sense, NCS closely resembles W. Ostwaldユs system. However, the fact that Ostwald System satndardizes physical reality while NCS standardizes psychological reality, clearly distinguishes the two. In its attempt to indicate color appearance itself by means of psychological expression, NCS psychometrically measures quantitative color perception to compose and indicate color notation by a psychometrical scale.
The notation is made not of hues deriving from pigments or a Maxwellユs color disc. The criterion for judgement is the colors learnt by the heart since oneユs childhood. As the naming with the word メNaturalモ suggests, color which are naturally felt and seen are inscribed and therefore, the color notation changes with the variation in lighting conditions and or other conditions under which an object is seen, through within the same color chart. NCS expresses color appearance by the degree of perception of the six psychological base colors. The six are yellow, red, blue, green, white and black. These are six colors which have made impressions on the heart, and are called basic colors. In-between colors are indicated by the psychological ratio of the two basic colors involved. In this case, a color cannot simultaneously have a tincture of yellow and a tincture of blue, and the same applies to colors between red and green.
Therefore, a color would carry a maximum of four basic attributes belonging to two chromatic elementary colors, plus white and black. Furthermore, a color has three different characteristics, a tincture of chromatic colors, and tints of white and black, with the total, numerically indicated, as 100. A tincture is indicated by the percentage of the two chromatic colors. Color notation is expressed in the order of the percentage of blackishness, that of tincture, and finally, of chromatic elementary colors. Because whiteness can be sought simply by subtracting the percentage of blackishness and the percentage of tinctures from 100, it is not included in the color notation. As an example, a chromatic colorユs notation of メ3050R40Bモ signifies that the amount of black tint is 30%, and that of primary color tincture is 50% (thus, the amount of white tint would be 20%), and that the tincture is a color that is 40/100 closer to blue and away from red (thus, the amount of red tincture is 60%). Another way of expressing this particular color is that it is a color that is perceived as being blakishness 30% + reddishness 30% + bluishness 20% + whiteness 20%.
NCS is published in the form of a Colour atlas (SS 01 91 02) by the Swedish Standard Institution. NCS is applicable to colors of an objectユs surface, but due to its nature as psychological system, its color atlas can be used as a proper color sample only under prescribed lighting and observation conditions.
Furthermore, it is said that the use of NCS as an emotional space model, has spread widely among designers, architects and those engaged in painting in the Scandinavian countries and other parts of the world. Colors are easily imaginable from symbols, and inversely, symbolization can be accomplished without difficulty at the sight of colors, facilitating the explanation of various perceptive phenomena. But on the other hand, NCS also has its shortcomings: it does not offer a uniform perceptual color space, has theoretically no physical standard for objects, and is incompatible with device-oriented color measurement.


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ABC Tone System --- Handicraft of the Color Solid
The three dimensions of color could indicate the surface color of an object precisely. The three dimensions mentioned here specify the hue, value and chroma. However, on the scenes where color schemes are instructed or in the fields of fashion or designs the properties that combine value and chroma are often called value/chroma tone so that the technique of specifying the hue and tone by two dimensions is prevalent. This is due to the effect of making it easier to handle and understand colors by expressing the three dimensionally distributed colors in plane definition.
The Tone System is the color grouping system and therefore, various kinds of categorical systems could exist according to the position of handling the colors.
In Japan, the Systematic Color Name Chart regulated in the JIS Z8102 メNames of non-luminous object coloursモ and the PCCS (Practical Color Co-ordinate System) are widely used. There is the ISCC-NBS Color Name Chart in the U.S.A.
The ABC (Address Book of Color) Tone System (originated by Professor KITABATAKE Akira of Bunka Womenユs University) is the latest tone system and was initially introduced into the world through the adoption into the 1999 edition of the Japan Paint Manufacturers Association Standard Paint Colors. This tone system is estimated to rise swiftly to fame coupled with the wide distribution of this book.
Much importance was attached to the color distribution in industrial paint or materials for fashion/interior decoration so that the ABC Tone System established the off neutral area between the achromatic and chromatic colors. According to this system, the achromatic colors between white and black were classified into 5 tones and the chromatic colors were classified into 19 tones. Added to which, the color chart system of the Japan Paint Manufacturers Association Standard Paint Colors was combined to give birth to a color order system that places importance on practicality.
The color solid is a tool produced to communicate visually and to understand at a glance that the color system is constructed in the form of three-dimensional solid color space.


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7 Colors Printing System Designer's Color Atlas [ DCA ]
Designerユs Color Atlas is a color system for the reproduction of colors in printing.
Color reproduction in printing progresses through what is called a 4 colors process printing method, and most print items are printed through this method. Theoretically, the 4 colors process printing method of cyan, magenta, yellow and black colors produces little defects. However, at the moment, the purity of the printing ink color is lower than the theoretical value, resulting in color domains that cannot be reproduced. This is seen as an inevitable phenomenon and for luxury print items, special colors are used to make up for this inadequacy or the 6 colors printing system with the addition of pale magenta and pale cyan is being used.
7 Colors Printing System was conceived as a color reproduction method in printing to supplement the above shortcoming. It has been made into a color sample book titled Designerユs Color Atlas (DCA), and has become a color order system.
This 7 Colors Printing System uses primary ink colors of cyan, magenta, yellow and black which are used in the 4 colors process printing system and additional 3 colors of orange, green and violet.In this 7 Colors Printing System, color is reproduced by layer-printing the 2 colors which are next to each other in the hue circle of the 6 chromatic primary colors or by combining the aforementioned 6 colors with black. To reproduce colors in printing, a highly transparent printing ink is used.

The density of the ink that is transferred onto the paper is adjusted by changing the dot dimensions or depth of plate and reproducing the target color through pointillism mixture and subtraction mixture in layer-printing. A color with a high degree of chroma particularly needs to have large dot dimensions, so it is mostly the subtraction mixture that is employed. The decrease in chroma accelerates with the increase in hue disagreement between the primary ink colors.
Thus, in a 4 colors process printing system, the performance of color reproduction deteriorates in the orange, green and violet color domains. 7 Colors Printing System was developed as a solution to this shortcoming.
The structure of the color dimension in a 7 Colors Printing System is one that was derived from combining a star-shaped plane of 6 primary colors that were arranged into 6 points as shown in the illustration and an equal dot-surface of black ink, etc. or in other words, equal black content surface. Itユs in the shape of a star consisting of 6-angled reverse pyramids whose peak is the 0% black ink dot surface and that converges on a single point of 100% black ink.
A psychological observation of the position-relationships between these 6 chromatic primary colors in the hue circle shows that the colors were arranged with equal space between them, the 3 colors of cyan, magenta and yellow, standard Japan colors, are used as is, each color ink is of high-degree transparency and the 3 colors that are positioned in the middle were established under the condition of having similar density and such. The differences in angle between each primary color are represented on the Munsell hue circle as follows: 50 degrees between magenta and orange, 75 degrees between orange and yellow, 85 degrees between yellow and green, 55 degrees between green and cyan, 45 degrees between cyan and violet and 50 degrees between violet and magenta.
For color printing using a dot screen, 4 types of screen angles were established to avoid the moir? phenomenon: 15 degrees, 45 degrees, 75 degrees and 90 degrees. Each of the angles were fitted to a color. Thus 4 angles is seen to be the limit. In 7 colors printing, it is possible to avoid the moir? phenomenon since the 2 colors on the opposing angular lines do not co-exist in any small domain. Thus, the same screen angle can be established for the 2 colors on the opposing angular line.
The patent to this 7 Colors Printing System is owned by Dainichiseika Color & Chemicals as メa printing method that is outstanding for the color reproduction of high degree chroma.モ

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