Subtractive color

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Subtractive color mixing SubtractiveColor.svg
Subtractive color mixing
An 1877 color photo by Louis Ducos du Hauron, a French pioneer of color photography. The overlapping subtractive yellow, cyan and red (magenta) image elements can be seen clearly along the edges of the image. Duhauron1877.jpg
An 1877 color photo by Louis Ducos du Hauron, a French pioneer of color photography. The overlapping subtractive yellow, cyan and red (magenta) image elements can be seen clearly along the edges of the image.

Subtractive color or subtractive color mixing predicts the spectral power distribution of light after it passes through successive layers of partially absorbing media. This idealized model is the essential principle of how dyes and pigments are used in color printing and photography, where the perception of color is elicited after white light passes through microscopic "stacks" of partially absorbing media allowing some wavelengths of light to reach the eye and not others, and also in painting, whether the colors are mixed or applied in successive layers.

Contents

Process

The subtractive color mixing model predicts the resultant spectral power distribution of light filtered through overlaid partially absorbing materials on a reflecting or transparent surface. Each layer partially absorbs some wavelengths of light from the illumination spectrum while letting others pass through, resulting in a colored appearance. The resultant spectral power distribution is predicted by sequentially taking the product of the spectral power distributions of the incoming light and transmissivity at each filter. [1]

Painting

The subtractive model also predicts the color resulting from a mixture of paints, or similar medium such as fabric dye, whether applied in layers or mixed together prior to application. In the case of paint mixed before application, incident light interacts with many different pigment particles at various depths inside the paint layer before emerging. [2] Art supply manufactures offer colors that successfully fill the roles of the subtractive primary colors magenta and cyan. For example, the phthalocyanine blues, which became available during the 1930s, and quinacridone magenta, first offered during the 1950s, together with yellow produce more highly-saturated violets and greens than do the traditional red and blue.

RYB

An RYB color wheel BYR color wheel.svg
An RYB color wheel

RYB (red, yellow, blue) is the traditional set of primary colors used for mixing pigments. It is used in art and art education, particularly in painting. It predated modern scientific color theory.

Red, yellow, and blue are the primary colors of the RYB color "wheel". The secondary colors, violet (or purple), orange, and green (VOG) make up another triad, conceptually formed by mixing equal amounts of red and blue, red and yellow, and blue and yellow, respectively.

Classification of pigment colors Pigment Colours - Classification.jpg
Classification of pigment colors

The RYB primary colors became the foundation of 18th-century theories of color vision as the fundamental sensory qualities blended in the perception of all physical colors and equally in the physical mixture of pigments or dyes. These theories were enhanced by 18th-century investigations of a variety of purely psychological color effects, in particular, the contrast between "complementary" or opposing hues produced by color afterimages and in the contrasting shadows in colored light. These ideas and many personal color observations were summarized in two founding documents in color theory: the Theory of Colours (1810) by the German poet and government minister Johann Wolfgang von Goethe, and The Law of Simultaneous Color Contrast (1839) by the French industrial chemist Michel Eugène Chevreul.

In late 19th and early to mid-20th-century commercial printing, use of the traditional RYB terminology persisted even though the more versatile CMY (cyan, magenta, yellow) triad had been adopted, with the cyan sometimes referred to as "process blue" and the magenta as "process red".

CMY and CMYK color models and printing processes

Cyan, magenta and yellow color filters CMY.jpg
Cyan, magenta and yellow color filters

In color printing, the usual primary colors are cyan, magenta and yellow (CMY). Cyan is the complement of red, meaning that the cyan serves as a filter that absorbs red. The amount of cyan ink applied to a white sheet of paper controls how much of the red light in white light will be reflected back from the paper. Ideally, the cyan ink is completely transparent to green and blue light and has no effect on those parts of the spectrum. Magenta is the complement of green, and yellow the complement of blue. Combinations of different amounts of the three inks can produce a wide range of colors with good saturation.

In inkjet color printing and typical mass production photomechanical printing processes, a black ink K (Key) component is included, resulting in the CMYK color model. The black ink serves to cover unwanted tints in dark areas of the printed image, which result from the imperfect transparency of commercially practical CMY inks; to improve image sharpness, which tends to be degraded by imperfect registration of the three color elements; and to reduce or eliminate consumption of the more expensive color inks where only black or gray is required.

Purely photographic color processes almost never include a K component, because in all common processes the CMY dyes used are much more perfectly transparent, there are no registration errors to camouflage, and substituting a black dye for a saturated CMY combination, a trivial prospective cost-benefit at best, is technologically impractical in non-electronic analog photography.

See also

Related Research Articles

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Color or colour is the visual perception based on the electromagnetic spectrum. Though color is not an inherent property of matter, color perception is related to an object's light absorption, reflection, emission spectra and interference. For most humans, colors are perceived in the visible light spectrum with three types of cone cells (trichromacy). Other animals may have a different number of cone cell types or have eyes sensitive to different wavelength, such as bees that can distinguish ultraviolet, and thus have a different color sensitivity range. Animal perception of color originates from different light wavelength or spectral sensitivity in cone cell types, which is then processed by the brain.

<span class="mw-page-title-main">Cyan</span> Color visible between blue and green on the visible spectrum; subtractive (CMY) primary color

Cyan is the color between blue and green on the visible spectrum of light. It is evoked by light with a predominant wavelength between 490 and 520 nm, between the wavelengths of green and blue.

<span class="mw-page-title-main">RGB color model</span> Color model based on red, green, and blue

The RGB color model is an additive color model in which the red, green and blue primary colors of 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.

<span class="mw-page-title-main">CMYK color model</span> Subtractive color model, used in color printing

The CMYK color model is a subtractive color model, based on the CMY color model, used in color printing, and is also used to describe the printing process itself. The abbreviation CMYK refers to the four ink plates used: cyan, magenta, yellow, and key (black).

<span class="mw-page-title-main">Primary color</span> Sets of colors that can be mixed to produce gamut of colors

A set of primary colors or primary colours consists of colorants or colored lights that can be mixed in varying amounts to produce a gamut of colors. This is the essential method used to create the perception of a broad range of colors in, e.g., electronic displays, color printing, and paintings. Perceptions associated with a given combination of primary colors can be predicted by an appropriate mixing model that reflects the physics of how light interacts with physical media, and ultimately the retina.

<span class="mw-page-title-main">Magenta</span> Color

Magenta is a purplish-red color. On color wheels of the RGB (additive) and CMY (subtractive) color models, it is located precisely midway between violet and red. It is one of the four colors of ink used in color printing by an inkjet printer, along with yellow, cyan, and black to make all the other colors. The tone of magenta used in printing, printer's magenta, is redder than the magenta of the RGB (additive) model, the former being closer to rose.

<span class="mw-page-title-main">Additive color</span> Model for predicting color created by mixing visible light

Additive color or additive mixing is a property of a color model that predicts the appearance of colors made by coincident component lights, i.e. the perceived color can be predicted by summing the numeric representations of the component colors. Modern formulations of Grassmann's laws describe the additivity in the color perception of light mixtures in terms of algebraic equations. Additive color predicts perception and not any sort of change in the photons of light themselves. These predictions are only applicable in the limited scope of color matching experiments where viewers match small patches of uniform color isolated against a grey or black background.

<span class="mw-page-title-main">Complementary colors</span> Pairs of colors losing hue when combined

Complementary colors are pairs of colors which, when combined or mixed, cancel each other out 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".

<span class="mw-page-title-main">Gamut</span> Color reproduction capability

In color reproduction and colorimetry, a gamut, or color gamut, is a convex set containing the colors that can be accurately represented, i.e. reproduced by an output device or measured by an input device. Devices with a larger gamut can represent more colors. Similarly, gamut may also refer to the colors within a defined color space, which is not linked to a specific device. A trichromatic gamut is often visualized as a color triangle. A less common usage defines gamut as the subset of colors contained within an image, scene or video.

Color theory, or more specifically traditional color theory, is the historical body of knowledge describing the behavior of colors, namely in color mixing, color contrast effects, color harmony, color schemes and color symbolism. Modern color theory is generally referred to as Color science. While there is no clear distinction in scope, traditional color theory tends to be more subjective and have artistic applications, while color science tends to be more objective and have functional applications, such as in chemistry, astronomy or color reproduction. Color theory dates back at least as far as Aristotle's treatise On Colors. A formalization of "color theory" began in the 18th century, initially within a partisan controversy over Isaac Newton's theory of color and the nature of primary colors. By the end of the 19th century, a schism had formed between traditional color theory and color science.

<span class="mw-page-title-main">Color wheel</span> Illustrative organization of color hues

A color wheel or color circle is an abstract illustrative organization of color hues around a circle, which shows the relationships between primary colors, secondary colors, tertiary colors etc.

<span class="mw-page-title-main">RYB color model</span> Subtractive color model

RYB is a subtractive color model used in art and applied design in which red, yellow, and blue pigments are considered primary colors. Under traditional color theory, this set of primary colors was advocated by Moses Harris, Michel Eugène Chevreul, Johannes Itten and Josef Albers, and applied by countless artists and designers. The RYB color model underpinned the color curriculum of the Bauhaus, Ulm School of Design and numerous art and design schools that were influenced by the Bauhaus, including the IIT Institute of Design, Black Mountain College, Design Department Yale University, the Shillito Design School, Sydney, and Parsons School of Design, New York.

Color printing or colour printing is the reproduction of an image or text in color.

<span class="mw-page-title-main">Secondary color</span> Color made by mixing two primary colors

A secondary color is a color made by mixing two primary colors of a given color model in even proportions. Combining two secondary colors in the same manner produces a tertiary color. Secondary colors are special in traditional color theory, but have no special meaning in color science.

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, taking account of visual perception, the resulting set of colors is called "color space."

<span class="mw-page-title-main">Carbon print</span> Photographic printing process

A carbon print is a photographic print with an image consisting of pigmented gelatin, rather than of silver or other metallic particles suspended in a uniform layer of gelatin, as in typical black-and-white prints, or of chromogenic dyes, as in typical photographic color prints.

<span class="mw-page-title-main">Color motion picture film</span> Photographic film type

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.

<span class="mw-page-title-main">Color mixing</span> Producing colors by combining the primary or secondary colors in different amounts

There are three types of color mixing models, depending on the relative brightness of the resultant mixture: additive, subtractive, and average. In these models, mixing black and white will yield white, black and gray, respectively. Physical mixing processes, e.g. mixing light beams or oil paints, will follow one or a hybrid of these 3 models. Each mixing model is associated with several color models, depending on the approximate primary colors used. The most common color models are optimized to human trichromatic color vision, therefore comprising three primary colors.

<span class="mw-page-title-main">Shades of magenta</span> Varieties of the color magenta

The color magenta has notable tints and shades. These various colors are shown below.

References

  1. Levoy, Marc. "Additive versus subtractive color mixing". graphics.stanford.edu. Retrieved 4 November 2020. On the other hand, if you reflect light from a colored surface, or if you place a colored filter in front of a light, then some of the wavelengths present in the light may be partially or fully absorbed by the colored surface or filter. If we characterize the light as an SPD, and we characterize absorption by the surface or filter using a spectrum of reflectivity or transmissivity, respectively, i.e. the percentage of light reflected or transmitted at each wavelength, then the SPD of the outgoing light can be computed by multiplying the two spectra. This multiplication is (misleadingly) called subtractive mixing.
  2. Williamson, Samuel J; Cummins, Herman Z (1983). Light and Color in Nature and Art. New York: John Wiley & Sons, Inc. pp. 28–30. ISBN   0-471-08374-7. Thus subtractive color mixing laws that successfully describe how light is altered by nonspectral filters also describes how light is altered by pigments.

Further reading