The Natural Color System (NCS) is a proprietary perceptual color model published by the Scandinavian Colour Institute (Skandinaviska Färginstitutet AB) of Stockholm, Sweden. It is based on the color opponency description of color vision, first proposed by German physiologist Ewald Hering. The system is usually used for matching colors (using printed reference cards), rather than mixing colors.

The underlying physiological mechanisms involved in color opponency include the bipolar and ganglion cells in the retina, which process the signal originated by the retinal cones before it is sent to the brain. A model like RGB describes what happens at the lower, retinal cone level, and thus is very well fitted for the task of "fooling the eye" as done by TV sets and computer displays. The NCS model, for its part, describes the organization of the color sensations as perceived at the upper, brain level, and thus is much better fitted than RGB to deal with how humans experience and describe their color sensations (hence the "natural" part of its name); but it would be useless, for example, for describing the behaviour of mixing lights and pigments.

The NCS is based on the six elementary color percepts of human vision—the psychological primaries—as described by color opponency—white, black, red, yellow, green, and blue—which are difficult to define perceptually in terms of others (for example, one cannot describe color red as looking "like a yellow and magenta mixture", even though you will in fact get a red pigment by mixing yellow and magenta pigments). These six elementary colors are frequently chosen to paint educational toys, or for designs that try to appeal from their simplicity (such as the Olympic flag and the Microsoft Windows logo). All the other perceptual colors are composite perceptions that can be defined in terms of those six (for example, turquoise looks like "bluegreen", orange like "a color that is both reddish and yellowish", and brown looks like "a very dark orange", that is, like a mixture of red, yellow and black). This all means the appearance of a color can be readily predicted from its NCS notation, whereas its notation in systems such as RGB often looks unintuitive (for example, yellow does not look like "a reddish-greenish color" at all, even though the yellow on an RGB monitor is obtained by mixing red and green lights). Note also that, under normal viewing circumstances, there is no hue that must be described as a mixture of opponent hues; that is, as a hue looking "redgreen" or "yellowblue" (see note in the color opponents article).

Colors in the NCS are defined by three values, specifying the amount of blackness (darkness), chromaticity (saturation), and a percentage value between two of the colours red, yellow, green or blue (hue). The blackness and the chromaticity together add up to less than or equal to 100%—their remainder from 100%, if any, gives the amount of whiteness. The complete NCS color notations can also be tagged with a letter giving the version of the NCS color standard that was used to specify the color.

Two examples of NCS color notation—the yellow and blue shades of the Swedish flag:

Yellow – NCS 0580-Y10R (= 5% darkness, 80% saturation, 90% yellow + 10% red = very slightly darkish mostly saturated yellow with a slight orangish tinge)

Blue – NCS 4055-R95B (= 40% darkness, 55% saturation, 5% red + 95% blue = somewhat dark rather unsaturated blue with a very slight purplish tinge)

The NCS is represented in 19 countries and is the reference norm for color designation in Sweden (since 1979), Norway (since 1984) and Spain (since 1994). It is also one of the standards used by the International Colour Authority, a leading publisher of color trend forecasts for the interior design and textile markets.

See also

Color chart, other color systems and charts

External links

Official NCS website

NCS Colour Centre for the UK and Ireland (an official distributor for the NCS)

An online NCS calculator

RGB Browser with NCS color matching

ToyPalette from Loo & Cox, a web application for generating color palettes from images. NCS color analysis of digital image.

ca:Natural Color System da:Natural Color System de:Natural Color System fr:Natural Color System it:Natural Color System lt:NCS nl:Natural Color System ja:ナチュラル・カラー・システム no:NCS pl:Natural Colour System ru:NCS sv:Natural Color System

A color model is an abstract mathematical model describing the way colors can be represented as tuples of numbers, typically as three or four values or color components. When this model is associated with a precise description of how the components are to be interpreted (viewing conditions, etc.), the resulting set of colors is called color space. This section describes ways in which human color vision can be modeled.

Tristimulus color space

One can picture this space as a region in three-dimensional Euclidean space if one identifies the ''x'', ''y'', and ''z'' axes with the stimuli for the long-wavelength (''L''), medium-wavelength (''M''), and short-wavelength (''S'') receptors. The origin, (''S'',''M'',''L'') = (0,0,0), corresponds to black. White has no definite position in this diagram; rather it is defined according to the color temperature or white balance as desired or as available from ambient lighting. The human color space is a horse-shoe-shaped cone such as shown here (see also CIE chromaticity diagram below), extending from the origin to, in principle, infinity. In practice, the human color receptors will be saturated or even be damaged at extremely high light intensities, but such behavior is not part of the CIE color space and neither is the changing color perception at low light levels (see: Kruithof curve).

The most saturated colors are located at the outer rim of the region, with brighter colors farther removed from the origin. As far as the responses of the receptors in the eye are concerned, there is no such thing as "brown" or "gray" light. The latter color names refer to orange and white light respectively, with an intensity that is lower than the light from surrounding areas. One can observe this by watching the screen of an overhead projector during a meeting: one sees black lettering on a white background, even though the "black" has in fact not become darker than the white screen on which it is projected before the projector was turned on. The "black" areas have not actually become darker but appear "black" relative to the higher intensity "white" projected onto the screen around it. See also color constancy.

The human tristimulus space has the property that additive mixing of colors corresponds to the adding of vectors in this space. This makes it easy to, for example, describe the possible colors (gamut) that can be constructed from the red, green, and blue primaries in a computer display.

CIE XYZ color space

:''Main article:'' CIE 1931 color space

One of the first mathematically defined color spaces is the CIE XYZ color space (also known as CIE 1931 color space), created by the International Commission on Illumination in 1931. These data were measured for human observers and a 2-degree field of view. In 1964, supplemental data for a 10-degree field of view were published.

Note that the tabulated sensitivity curves have a certain amount of arbitrariness in them. The shapes of the individual X, Y and Z sensitivity curves can be measured with a reasonable accuracy. However, the overall luminosity curve (which in fact is a weighted sum of these three curves) is subjective, since it involves asking a test person whether two light sources have the same brightness, even if they are in completely different colors. Along the same lines, the relative magnitudes of the X, Y, and Z curves are arbitrary. One could as well define a valid color space with an X sensitivity curve that has twice the amplitude. This new color space would have a different shape. The sensitivity curves in the CIE 1931 and 1964 xyz color space are scaled to have equal areas under the curves.

Sometimes XYZ colors are represented by the luminance, Y, and chromaticity coordinates ''x'' and ''y'', defined by:

:

Mathematically, ''x'' and ''y'' are projective coordinates and the colors of the chromaticity diagram occupy a region of the real projective plane. Because the CIE sensitivity curves have equal areas under the curves, light with a flat energy spectrum corresponds to the point (''x'',''y'') = (0.333,0.333).

The values for ''X'', ''Y'', and ''Z'' are obtained by integrating the product of the spectrum of a light beam and the published color-matching functions.

RGB color model

Media that transmit light (such as television) use additive color mixing with primary colors of red, green, and blue, each of which stimulates one of the three types of the eye's color receptors with as little stimulation as possible of the other two. This is called "RGB" color space. Mixtures of light of these primary colors cover a large part of the human color space and thus produce a large part of human color experiences. This is why color television sets or color computer monitors need only produce mixtures of red, green and blue light. See Additive color.

Other primary colors could in principle be used, but with red, green and blue the largest portion of the human color space can be captured. Unfortunately there is no exact consensus as to what loci in the chromaticity diagram the red, green, and blue colors should have, so the same RGB values can give rise to slightly different colors on different screens.

HSV and HSL representations

Recognizing that the geometry of the RGB model is poorly aligned with the color-making attributes recognized by human vision, computer graphics researchers developed two alternate representations of RGB, HSV and HSL (''h''ue, ''s''aturation, ''v''alue and ''h''ue, ''s''aturation, ''l''ightness), in the late 1970s. HSV and HSL improve on the color cube representation of RGB by arranging colors of each hue in a radial slice, around a central axis of neutral colors which ranges from black at the bottom to white at the top. The fully saturated colors of each hue then lie in a circle, a color wheel.

HSV models itself on paint mixture, with its saturation and value dimensions resembling mixtures of a brightly colored paint with, respectively, white and black. HSL tries to resemble more perceptual color models such as NCS or Munsell. It places the fully saturated colors in a circle of lightness ½, so that lightness 1 always implies white, and lightness 0 always implies black.

HSV and HSL are both widely used in computer graphics, particularly as color pickers in image editing software. The mathematical transformation from RGB to HSV or HSL could be computed in real time, even on computers of the 1970s, and there is an easy-to-understand mapping between colors in either of these spaces and their manifestation on a physical RGB device.

CMYK color model

It is possible to achieve a large range of colors seen by humans by combining cyan, magenta, and yellow transparent dyes/inks on a white substrate. These are the ''subtractive'' primary colors. Often a fourth black is added to improve reproduction of some dark colors. This is called "CMY" or "CMYK" color space.

The cyan ink absorbs red light but transmits green and blue, the magenta ink absorbs green light but transmits red and blue, and the yellow ink absorbs blue light but transmits red and green. The white substrate reflects the transmitted light back to the viewer. Because in practice the CMY inks suitable for printing also reflect a little bit of color, making a deep and neutral black impossible, the K (black ink) component, usually printed last, is needed to compensate for their deficiencies. The dyes used in traditional color photographic prints and slides are much more perfectly transparent, so a K component is normally not needed or used in those media.

Color systems

There are various types of color systems that classify color and analyse their effects. The American Munsell color system devised by Albert H. Munsell is a famous classification that organises various colors into a color solid based on hue, saturation and value. Other important color systems include the Swedish Natural Color System (NCS) from the Scandinavian Color Institute, the Optical Society of America's Uniform Color Space (OSA-UCS), and the Hungarian Coloroid system developed by Antal Nemcsics from the Budapest University of Technology and Economics. Of those, the NCS is based on the opponent-process color model, while the Munsell, the OSA-UCS and the Coloroid attempt to model color uniformity. The American Pantone and the German RAL commercial color-matching systems differ from the previous ones in that their color spaces are not based on an underlying color model.

Other uses of "color model"

Models of mechanism of color vision

We also use "color model" to indicate a model or mechanism of color vision for explaining how color signals are processed from visual cones to ganglion cells. For simplicity, we call these models color mechanism models. The classical color mechanism models are Young-Helmholtz's trichromatic model and Hering's opponent-process model. Though these two theories were initially thought to be at odds, it later came to be understood that the mechanisms responsible for color opponency receive signals from the three types of cones and process them at a more complex level.

Vertebrate evolution of color vision

Vertebrate animals were primitively tetrachromatic. They possessed four types of cones--long, mid, short wavelength cones, and ultraviolet sensitive cones. Today, fish, reptiles and birds are all tetrachromatic. Placental mammals lost both the mid and short wavelength cones. Thus, most mammals do not have complex color vision--they are dichromatic but they are sensitive to ultraviolet light, though they cannot see its colors. Human trichromatic color vision is a recent evolutionary novelty that first evolved in the common ancestor of the Old World Primates. Our trichromatic color vision evolved by duplication of the long wavelength sensitive opsin, found on the X chromosome. One of these copies evolved to be sensitive to green light and constitutes our mid wavelength opsin. At the same time, our short wavelength opsin evolved from the ultraviolet opsin of our vertebrate and mammalian ancestors.

Human red-green color blindness occurs because the two copies of the red and green opsin genes remain in close proximity on the X chromosome. Because of frequent recombination during meiosis, these gene pairs can get easily rearranged, creating versions of the genes that do not have distinct spectral sensitivities.

References

See also

Color space

Color

External links

Illustrations and summaries of RGB, CMYK, LAB, HSV, HSL, and NCS

ar:نموذج لوني ca:Model de color cs:Barevný model fr:Modèle colorimétrique it:Modello di colore no:Fargemodell ru:Цветовая модель sk:Farebný model sl:Barvni model uk:Кольорова модель

''Natural Color'' was a term used in the beginning of film and later on in the 1920s, and early 1930s as a color film process that actually filmed color images, rather than a color tinted or colorized movie. The first natural color processes were in the 1900s and 1910s and were two color additive color processes or red and green missing primary color blue, one additive process of time was Kinemacolor. By the 1920s, subtractive color was mostly in use with such processes as Technicolor, Prizma and Multicolor, but Multicolor was mostly never in use in the late 1920s, Technicolor was mostly in use. The only one who cared to mess with Multicolor was William Fox, probably because Multicolor was more cheaper of a process and at the time in 1929 William Fox was in debt. The difference between additive color and subtractive color were that a additive color film required a special projector that could project two componets of film at the same time, a green record and a red record. But additive color didn't required a special projector, the two pieces of film was chemically formed together and was projected in one strip of film.

One of the first movies to use subtractive color was a silent film titled ''Cupid Angling'' (1918). In 1932, Walt Disney made the first film to use a red, green and blue color process (Technicolor), ''Flowers and Trees''. Two years later, the first feature film to use three-color Technicolor was made, titled ''The Cat and the Fiddle'' (1934), a partial color movie. In 1935, the first feature length movie to be filmed entirely in 3-color Technicolor was ''Becky Sharp''.

1900-1909

1910s

The first color features were made in the 1910s. The very first was ''With Our King and Queen Through India'' (1912). In 1917, Technicolor made their first film, a two-color additive film entitled ''The Gulf Between'' (1917), ''The Gulf Between'' was also the first color feature in America, but rather than being filmed in Hollywood it was actually filmed in Jacksonville Florida. Today ''The Gulf Between'' is lost.

1920s

In 1922, Technicolor made their second feature and also the first movie made in their second color process, called process 2. The movie was ''The Toll of the Sea''. It was the first color feature made in Hollywood. The movie starred Anna May Wong. Wong never thought the movie would ever make it to the screen, but it did. In 1923, Paramount Pictures made the Cecil B. De Mille partial Technicolor epic ''The Ten Commandments'', which would be remade 33 years later by DeMille in 1956, also in color by Technicolor. Also in 1923, Prizma was used to film the 1923 version of ''Vanity Fair''. The third feature to be filmed entirely in color by Technicolor was ''Wanderer of the Wasteland'', today a lost film, released in 1924. It was advertised as being filmed in 100% Natural Color. Technicolor made many more silent films in color through the years, but in 1929, the first talking picture to use a color (Technicolor) sequence was ''The Broadway Melody''. The color hues of that sequence are lost; the sequence only survives in black and white television prints from the 1950s. That year, Warner Bros. made the first all color-all talking movie, ''On With the Show'', which also only survives in black and white, with only a small fragment of surviving color, found in 2005. Later in 1929, the first color talking movies were being made, such as ''Paris'' (Warner Bros.), ''Rio Rita'' (RKO, first RKO color movie, color sequenced]]), ''Sally'' (Warner Bros., third all color-all talking feature), ''Gold Diggers of Broadway'' (Warner Bros., second all color-all talking feature), ''The Hollywood Revue'' (MGM's second musical, after ''The Broadway Melody'') and many more. Most of the color talking movies made in 1929 mostly survive in 1950s black and white television copies or with color sequences cut. In 1929, Technicolor was so busy filming color movies that the Warner Bros. musical revue ''The Show of Shows'' (1929), which was originally going to be filmed in full color, had to be filmed only mostly in color, with 21 minutes in black and white, a seventeen minute section of part one and a four minute opening of part two. While most companies used Technicolor, William Fox, owner of Fox Movie Corporation, used Multicolor.

1930s

Color movies released in 1930 included ''The Life of the Party'' (Warner Bros.), ''Under a Texas Moon'' (Warner Bros.), ''Children of Pleasure'' (MGM), ''Chasing Rainbows'' (MGM), ''Show Girl in Hollywood'' (Warner Bros., one of Al Jolson's first color appearances), ''Viennese Nights'' (Warner Bros.), ''Hit the Deck'' (RKO Radio Pictures), and ''Leathernecking'' (RKO), ''The Cuckoos'' (RKO). Like 1929, the original color negatives for many movies of the year are considered to be lost and only survive in black and white due to the studios wanting more space in their film vaults so they threw away the films and aired them on black and white television before, but some color movies from this time have been found throughout the years.

In 1932, Walt Disney released the first three-color Technicolor film, ''Flowers and Trees''. Two years later, MGM made ''The Cat and the Fiddle'', starring Jeanette MacDonald, the first feature film to partially use three color Technicolor. 1939, which is considered by many film buffs as Hollywood's greatest year, had hits in color, such as ''The Wizard of Oz'', ''The Women'', ''Dodge City'' and the most successful of them all, ''Gone with the Wind''.

Color film processes

See also

List of early color feature films

''His Supreme Moment'' (1925)

Category:Film and video technology