Additive color

Additive color is a method to create color by mixing a number of different light colors, with shades of red, green, and blue being the most common primary colors used in the additive color system.

Additive color is in contrast to subtractive color, in which colors are created by subtracting (absorbing) parts of the spectrum of light present in ordinary white light, by means of colored pigments or dyes, such as those in paints, inks, and the three dye layers in typical color photographs on film.

The combination of two of the standard three additive primary colors in equal proportions produces an additive secondary colorcyan, magenta or yellow—which, in the form of dyes or pigments, are the standard primary colors in subtractive color systems. The subtractive system using primaries that are the secondaries of the additive system can be viewed as an alternative approach to reproducing a wide range of colors by controlling the relative amounts of red, green, and blue light that reach the eye.

Computer monitors and televisions are the most common examples of additive color. Examination with a sufficiently powerful magnifying lens will reveal that each pixel in CRT, LCD and most other types of color video displays is composed of red, green and blue sub-pixels, the light from which combines in various proportions to produce all the other colors as well as white and shades of gray. The colored sub-pixels do not overlap on the screen, but when viewed from a normal distance they overlap and blend on the eye's retina, producing the same result as external superimposition.

Another example of additive color can be found in the overlapping projected colored lights often used in theatrical lighting for plays, concerts, circus shows and night clubs.[1]

The full gamut of color available in any additive color system is defined by all the possible combinations of all the possible luminosities of each primary color in that system. In chromaticity space, the gamut is a plane convex polygon with corners at the primaries. For three primaries, it is a triangle.

Results obtained when mixing additive colors are often counterintuitive for people accustomed to the subtractive color system of pigments, dyes, inks and other substances that present color to the eye by reflection rather than emission. For example, in subtractive color systems, green is a combination of yellow and cyan; in additive color, red plus green makes yellow. Additive color is a result of the way the eye detects color, and is not a property of light. There is a vast difference between a pure spectral yellow light, with a wavelength of approximately 580 nm, and a mixture of red and green light. However, both stimulate our eyes in a similar manner, so we do not detect that difference, and both are yellow light to the human eye. (See eye (cytology), color vision.)

AdditiveColor
Additive color mixing: adding red to green yields yellow; adding all three primary colors together yields white.
J C Maxwell with top
James Clerk Maxwell, with his color top that he used for investigation of color vision and additive color

History

Tartan Ribbon
The first permanent color photograph, taken by Thomas Sutton, under the direction of James Clerk Maxwell in 1861.

Systems of additive color are motivated by the Young–Helmholtz theory of trichromatic color vision, which was articulated around 1850 by Hermann von Helmholtz, based on earlier work by Thomas Young. For his experimental work on the subject, James Clerk Maxwell is sometimes credited as being the father of additive color.[2] He had the photographer Thomas Sutton photograph a tartan ribbon on black-and-white film three times, first with a red, then green, then blue color filter over the lens. The three black-and-white images were developed and then projected onto a screen with three different projectors, each equipped with the corresponding red, green, or blue color filter used to take its image. When brought into alignment, the three images (a black-and-red image, a black-and-green image and a black-and-blue image) formed a full color image, thus demonstrating the principles of additive color.[3]

Examples

RGB illumination
Red, green, and blue lights combining by reflecting from a white wall.
RGB additiv
Additive mixing of primary colors by proximity: red, green, and blue lines brought close together create mixed colors. (Click image to enlarge and see the effect clearly.)
Additive color mixing
Additive color mixing

The following chart demonstrates an example of the mixing and perception of additive primaries, step by step.

Light source Green (medium wavelength) light and red (long wavelength) light radiate from two different projectors.
Projection screen Both the green and the red light reflect off of a spot on the screen.
Retina The mixed light activates the M and L cones on a spot on the retina about equally.
Brain The brain interprets the equal amounts of M and L signal as yellow.

To fully understand the process, it should be demonstrated how dull colors are obtained using cyan, magenta, and yellow instead of red, green, and blue.

Light source Cyan (short to medium wavelengths) and yellow (medium to long wavelengths) light radiate from two different projectors.
Projection screen Both the cyan and yellow reflect off of a spot on the screen.
Retina M cones on a spot on the retina are strongly activated by both the cyan and yellow light, while S cones are activated by cyan and L cones by yellow.
Brain The brain receives signals from the cones about some short, lots of medium, and some long wavelengths. It interprets the signal as pale (unsaturated) green.

See also

Additive color mixing with CD covers

References

  1. ^ David Briggs (2007). "The Dimensions of Color". Archived from the original on 2015-09-28. Retrieved 2011-11-23.
  2. ^ "James Clerk Maxwell". Inventor's Hall of Fame, Rochester Institute of Technology Center for Imaging Science. Archived from the original on 2010-09-18.
  3. ^ Robert Hirsch (2004). Exploring Colour Photography: A Complete Guide. Laurence King Publishing. ISBN 1-85669-420-8. Archived from the original on 2017-02-25.

External links

CMYK color model

The CMYK color model (process color, four color) is a subtractive color model, used in color printing, and is also used to describe the printing process itself. CMYK refers to the four inks used in some color printing: cyan, magenta, yellow, and key.

The CMYK model works by partially or entirely masking colors on a lighter, usually white, background. The ink reduces the light that would otherwise be reflected. Such a model is called subtractive because inks "subtract" the colors red, green and blue from white light. White light minus red leaves cyan, white light minus green leaves magenta, and white light minus blue leaves yellow.

In additive color models, such as RGB, white is the "additive" combination of all primary colored lights, while black is the absence of light. In the CMYK model, it is the opposite: white is the natural color of the paper or other background, while black results from a full combination of colored inks. To save cost on ink, and to produce deeper black tones, unsaturated and dark colors are produced by using black ink instead of the combination of cyan, magenta, and yellow.

Color mixing

There are two types of color mixing: Additive and Subtractive. In both cases, there are three primary colors, three secondary colors (colors made from 2 of the three primary colors in equal amounts), and one tertiary color made from all three primary colors. This point is a common source of confusion, as there are different sets of primary colors depending on whether you are working with additive or subtractive mixing.

Color motion picture film

Color motion picture film refers both to unexposed color photographic film in a format suitable for use in a motion picture camera, and to finished motion picture film, ready for use in a projector, which bears images in color.

The first color cinematography was by additive color systems such as the one patented by Edward Raymond Turner in 1899 and tested in 1902. A simplified additive system was successfully commercialised in 1909 as Kinemacolor. These early systems used black-and-white film to photograph and project two or more component images through different color filters.

Around 1920, the first practical subtractive color processes were introduced. These also used black-and-white film to photograph multiple color-filtered source images, but the final product was a multicolored print that did not require special projection equipment. Before 1932, when three-strip Technicolor was introduced, commercialized subtractive processes used only two color components and could reproduce only a limited range of color.

In 1935, Kodachrome was introduced, followed by Agfacolor in 1936. They were intended primarily for amateur home movies and "slides". These were the first films of the "integral tripack" type, coated with three layers of differently color-sensitive emulsion, which is usually what is meant by the words "color film" as commonly used. The few color films still being made in the 2010s are of this type. The first color negative films and corresponding print films were modified versions of these films. They were introduced around 1940 but only came into wide use for commercial motion picture production in the early 1950s. In the US, Eastman Kodak's Eastmancolor was the usual choice, but it was often re-branded with another trade name, such as "WarnerColor", by the studio or the film processor.

Later color films were standardized into two distinct processes: Eastman Color Negative 2 chemistry (camera negative stocks, duplicating interpositive and internegative stocks) and Eastman Color Positive 2 chemistry (positive prints for direct projection), usually abbreviated as ECN-2 and ECP-2. Fuji's products are compatible with ECN-2 and ECP-2.

Film was the dominant form of cinematography until the 2010s, when it was largely replaced by digital cinematography.

Color theory

In the visual arts, color theory or colour theory is a body of practical guidance to color mixing and the visual effects of a specific color combination. There are also definitions (or categories) of colors based on the color wheel: primary color, secondary color, and tertiary color. Although color theory principles first appeared in the writings of Leone Battista Alberti (c. 1435) and the notebooks of Leonardo da Vinci (c. 1490), a tradition of "colory theory" began in the 18th century, initially within a partisan controversy over Isaac Newton's theory of color (Opticks, 1704) and the nature of primary colors. From there it developed as an independent artistic tradition with only superficial reference to colorimetry and vision science.

Color triangle

A colour triangle is an arrangement of colours within a triangle, based on the additive combination of three primary colors at its corners.

An additive colour space defined by three primary colors has a chromaticity gamut that is a color triangle, when the amounts of the primaries are constrained to be nonnegative.Before the theory of additive color was proposed by Thomas Young and further developed by James Clerk Maxwell and Hermann von Helmholtz, triangles were also used to organize colors, for example around a system of red, yellow, and blue primary colors.After the development of the CIE system, color triangles were used as chromaticity diagrams, including briefly with the trilinear coordinates representing the chromaticity values. Since the sum of the three chromaticity values has a fixed value, it suffices to depict only two of the three values, using Cartesian co-ordinates. In the modern x,y diagram, the large triangle bounded by the imaginary primaries X, Y, and Z has corners (1,0), (0,1), and (0,0), respectively; colour triangles with real primaries are often shown within this space.

Complementary colors

Complementary colors are pairs of colors which, when combined or mixed, cancel each other out (lose hue) by producing a grayscale color like white or black. When placed next to each other, they create the strongest contrast for those two colors. Complementary colors may also be called "opposite colors."

Which pairs of colors are considered complementary depends on the color theory one uses:

Modern color theory uses either the RGB additive color model or the CMY subtractive color model, and in these, the complementary pairs are red–cyan, green–magenta, and blue–yellow.

In the traditional RYB color model, the complementary color pairs are red–green, yellow–purple, and blue–orange.

Opponent process theory suggests that the most contrasting color pairs are red–green, and blue–yellow.

Cyan

Cyan (, ) is a greenish-blue color. It is evoked by light with a predominant wavelength of between 490–520 nm, between the wavelengths of green and blue.In the subtractive color system, or CMYK (subtractive), which can be overlaid to produce all colors in paint and color printing, cyan is one of the primary colors, along with magenta, yellow, and black. In the additive color system, or RGB (additive) color model, used to create all the colors on a computer or television display, cyan is made by mixing equal amounts of green and blue light. Cyan is the complement of red; it can be made by the removal of red from white light. Mixing red light and cyan light at the right intensity will make white light.

The web color cyan is synonymous with aqua. Other colors in the cyan color range are teal, turquoise, electric blue, aquamarine, and others described as blue-green.

Index of color-related articles

This is a list of color topic-related articles.

For a list of articles about specific named colors, see list of colors.

Instant film

Instant film is a type of photographic film introduced by Polaroid to be used in an instant camera (and, with accessory hardware, many other professional film cameras). The film contains the chemicals needed for developing and fixing the photograph, and the instant camera exposes and initiates the developing process after a photo has been taken.

In earlier Polaroid instant cameras the film is pulled through rollers which breaks open a pod containing a reagent that is spread between the exposed negative and receiving positive sheet. This film sandwich develops for some time after which the positive sheet is peeled away from the negative to reveal the developed photo. In 1972, Polaroid introduced integral film, which incorporated timing and receiving layers to automatically develop and fix the photo without any intervention from the photographer.

Instant film is available in sizes from 24 mm × 36 mm (0.94 in × 1.42 in) (similar to 135 film) up to 50.8 cm × 61 cm (20 in × 24 in) size, with the most popular film sizes for consumer snapshots being approximately 83 mm × 108 mm (3.3 in × 4.3 in) (the image itself is smaller as it is surrounded by a border). Early instant film was distributed on rolls, but later and current films are supplied in packs of 8 or 10 sheets, and single sheet films for use in large format cameras with a compatible back.

Though the quality of integral instant film is not as good as conventional film, peel apart black and white film, and to a lesser extent color film approached the quality of traditional film types. Instant film was used where it was undesirable to have to wait for a roll of conventional film to be finished and processed, e.g., documenting evidence in law enforcement, in health care and scientific applications, and producing photographs for passports and other identity documents, or simply for snapshots to be seen immediately. Some photographers use instant film for test shots, to see how a subject or setup looks before using conventional film for the final exposure. Instant film is also used by artists to achieve effects that are impossible to accomplish with traditional photography, by manipulating the emulsion during the developing process, or separating the image emulsion from the film base. Instant film has been supplanted for most purposes by digital photography, which allows the result to be viewed immediately on a display screen or printed with dye sublimation, inkjet, or laser home or professional printers.

Instant film is notable for having had a wider range of film speeds available than other negative films of the same era, having been produced in ISO 4 to ISO 20,000. Current instant film formats typically have an ISO between 100 and 1000.Two companies manufacture instant film: Fujifilm (Instax integral film for its Instax cameras), and Polaroid Originals (previously named The Impossible Project) for older Polaroid cameras (600, SX-70, Spectra and 8×10) and its I-Type cameras.

Keller-Dorian cinematography

Keller-Dorian cinematography was a French technique from the 1920s for filming movies in color, using a lenticular process to separate red, green and blue colors and record them on a single frame of black-and-white film. This additive color system differs from other systems, for example Technicolor, which divided the colors into more than one frame on one or more pieces of film.

The system was used to film several scenes of Abel Gance's Napoléon (1927) and for La Femme et le pantin by Jacques de Baroncelli (1928). However, projection of this process in movie theaters seems to have been more difficult, so neither of these films was ever presented using this technique. Also, making prints was described by one source as "impossible."

This process was used by Eastman Kodak for the motion picture process Kodacolor, introduced in 1928 as the first amateur filmmaker's 16mm film color process available for the home movie market.

In about 1929 Ludwig Blattner bought the rights for the use outside the USA of the Keller-Dorian process, and this process was then known as the Blattner Keller-Dorian process, which lost out to rival colour systems.

Kodacolor (filmmaking)

In motion pictures, Kodak's Kodacolor brand was associated with an early lenticular (additive color) color motion picture process, first introduced in 1928 for 16mm film. The process was based on the Keller-Dorian system of lenticular color photography.

The process used a special panchromatic black-and-white film stock used with the emulsion away from the lens. The film base in front of the emulsion was embossed with a mass of tiny lenses, the purpose of which was to form small images of a striped filter which was attached to the camera lens. The filter had three colored stripes (red, green and blue-violet); when an exposure was made the varying proportion of each color reflected from the subject passed through the filter and was recorded on the film beneath each of the embossed lenses as areas of strips in groups of three, each strip varying in density according to the received color value (Dufaycolor used similar principles, but had the filter as part of the film itself).

Filming required the camera to be used at f/1.9 only, so that the striped filter worked correctly. The original Kodacolor film required an exposure of about a 1/30 second at f/1.9 in bright sunlight representing a film 'speed' (sensitivity) in modern terms of about 0.5 ISO. The physical movement of the film through the gate (frame-advance) requires additional time. The later Super Sensitive Kodacolor could be used "outdoors in any good photographic light, and even indoors under favourable conditions."

To project the film a projector was required fitted with the Kodacolor Projection Filter, which is similar in appearance the filter fitted to the camera. The lenticular image on the film is transformed into a natural color picture on the screen. As with most color processes involving a lenticular image the pattern intrudes, and there is noticeable light loss.

While Kodacolor was a popular color home movie format, it had several drawbacks. It could not yield multiple copies easily, special film was necessary to shoot with, and the additive image was colorful and clear, but inherently darker than subtractive processes.

Lenticular Kodacolor was phased out after the introduction of 16 mm Kodachrome film in 1935.

Natural color

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 an additive color film required a special projector that could project two components 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 were 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. Three years later, the first feature length movie to be filmed entirely in 3-color Technicolor was Becky Sharp.

Prizma

The Prizma Color system was a color motion picture process, invented in 1913 by William Van Doren Kelley and Charles Raleigh. Initially, it was a two-color additive color system, similar to its predecessor, Kinemacolor. However, Kelley eventually transformed Prizma into a bi-pack color system that itself became the predecessor for future color processes such as Multicolor and Cinecolor.

RGB color model

The RGB color model is an additive color model in which red, green and blue light are added together in various ways to reproduce a broad array of colors. The name of the model comes from the initials of the three additive primary colors, red, green, and blue.

The main purpose of the RGB color model is for the sensing, representation and display of images in electronic systems, such as televisions and computers, though it has also been used in conventional photography. Before the electronic age, the RGB color model already had a solid theory behind it, based in human perception of colors.

RGB is a device-dependent color model: different devices detect or reproduce a given RGB value differently, since the color elements (such as phosphors or dyes) and their response to the individual R, G, and B levels vary from manufacturer to manufacturer, or even in the same device over time. Thus an RGB value does not define the same color across devices without some kind of color management.

Typical RGB input devices are color TV and video cameras, image scanners, and digital cameras. Typical RGB output devices are TV sets of various technologies (CRT, LCD, plasma, OLED, quantum dots, etc.), computer and mobile phone displays, video projectors, multicolor LED displays and large screens such as JumboTron. Color printers, on the other hand are not RGB devices, but subtractive color devices (typically CMYK color model).

This article discusses concepts common to all the different color spaces that use the RGB color model, which are used in one implementation or another in color image-producing technology.

RGB color space

A RGB color space is any additive color space based on the RGB color model. A particular RGB color space is defined by the three chromaticities of the red, green, and blue additive primaries, and can produce any chromaticity that is the triangle defined by those primary colors. The complete specification of an RGB color space also requires a white point chromaticity and a gamma correction curve. As of 2007, sRGB is by far the most commonly used RGB color space.

RGB is an abbreviation for red–green–blue.

Subtractive color

A subtractive color model involves the mixing of a limited set of dyes, inks, paint pigments or natural colorants to create a wider range of colors, each the result of partially or completely subtracting (that is, absorbing) some wavelengths of light and not others. The color that a surface displays depends on which parts of the visible spectrum are not absorbed and therefore remain visible.

Subtractive color systems start with light, presumably white light. Colored inks, paints, or filters between the viewer and the light source or reflective surface subtract wavelengths from the light, giving it color. If the incident light is other than white, the viewer's brain is able to compensate well, but not perfectly, sometimes giving a flawed impression of the "true" color of the surface.

Additive color systems start with darkness. Light sources of various wavelengths are added in various proportions to produce a range of colors. Usually, three primary colors are combined to stimulate humans’ trichromatic color vision, sensed by the three types of cone cells in the eye, giving an apparently full range.

The World, the Flesh and the Devil (1914 film)

The World, the Flesh and the Devil (1914) is a British silent drama film. The film, now considered a lost film, was made using the additive color Kinemacolor process.

The title comes from the Book of Common Prayer: "From all the deceits of the world, the flesh, and the devil, spare us, good Lord."

Tints and shades

In color theory, a tint is a mixture of a color with white, which reduces darkness, while a shade is a mixture with black, which increases darkness. Both processes affect the resulting color mixture's relative lightness. A tone is produced either by mixing a color with grey, or by both tinting and shading. Mixing a color with any neutral color (including black, gray and white) reduces the chroma, or colorfulness, while the hue remains unchanged.

In common language, the term shade can be generalized to furthermore encompass any varieties of a particular color, whether technically they are shades, tints, tones, or slightly different hues. Meanwhile, the term tint can be generalized to refer to any lighter or darker variation of a color (e.g. tinted windows).When mixing colored light (additive color models), the achromatic mixture of spectrally balanced red, green, and blue (RGB) is always white, not gray or black. When we mix colorants, such as the pigments in paint mixtures, a color is produced which is always darker and lower in chroma, or saturation, than the parent colors. This moves the mixed color toward a neutral color—a gray or near-black. Lights are made brighter or dimmer by adjusting their brightness, or energy level; in painting, lightness is adjusted through mixture with white, black or a color's complement.

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