Color mixing

Last updated April 21, 2024

There are three types of color mixing models, depending on the relative brightness of the resultant mixture: additive, subtractive, and average.^[1] 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.^[1] 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.^[1]^: 4.2

Mixing models

Additive model

Additive mixing combines two or more colors into a mixture with brightness equal to the sum of the components' brightnesses.^[1]^: 4.4 An ideal physical model to demond lights aimed at the observer. The additive model is usually demonstrated by reflecting two beams of colored light off a white, matte surface (e.g. projectors) or by analyzing the sub-pixels of a color display, both of which follow the additive model closely.

The most common additive color model is the RGB color model, which uses three primary colors: red, green, and blue. This model is the basis of most color displays. Some modern displays are Multi-primary color displays, which have 4-6 primaries (RGB, plus cyan, yellow and/or magenta) in order to increase the size of the color gamut. For all additive color models, the absence of all primaries results in black. For practical additive color models, an equal superposition of all primaries results in neutral (gray or white). In the RGB model, an equal mixture of red and green is yellow, an equal mixture of green and blue is cyan and an equal mixture of blue and red is magenta.^[1]^: 4.2 Yellow, cyan and magenta are the secondary colors of the RGB model.

Subtractive model

A simulated example of (idealized) subtractive color mixing in the CMY model. The primaries cyan, magenta and yellow combine pairwise to produce subtractive secondaries red, green, and blue. Combining all three primaries (center) absorbs all light and produces black. In practical CMY color models, the center is usually dark gray and a separate black pigment is required to produce black (CMYK model). SubtractiveColorMixing.png — A simulated example of (idealized) subtractive color mixing in the CMY model. The primaries cyan, magenta and yellow combine pairwise to produce subtractive secondaries red, green, and blue. Combining all three primaries (center) absorbs all light and produces black. In practical CMY color models, the center is usually dark gray and a separate black pigment is required to produce black (CMYK model).

Subtractive mixing combines two or more colors into a mixture with brightness lower than either of the two components' brightnesses. An ideal physical model to demonstrate the subtractive model comprises a white light transmitting through two colored filters, each of which subtract a portion of the white light, transmitting a light of the combined color.^[1]^: 5.2 However, the subtractive model is usually demonstrated with dyes or pigments, such as paint or ink, which often do not closely follow the subtractive model. How well they follow the model depends mostly on the opacity of the pigment or dye.^[1]^: 6.1

The most common subtractive color models are the CMYK color model, CMY color model and RYB color model.^[1]^: 6.2 The CMYK model used in color printing uses cyan, magenta, yellow, and black primaries. For all subtractive color models, the absence of all color primaries results in white. For ideal subtractive color models, an equal superposition of all primaries results in a neutral (dark gray or black). The CMYK model adds a black primary to improve the darkness of blacks, where the CMY model can only mix to dark grey or only achieves black inefficiently, i.e. by using lots of the primary pigments. In the CMY model, an equal mixture of cyan and magenta is blue, an equal mixture of magenta and yellow is red and an equal mixture of yellow and cyan is green. These mixtures are the secondary colors of the CMY model, which are the same as the primaries of the additive RGB model and vice versa.

Average model

Average mixing (sometimes additive-average) combines two colors into a mixture with brightness equal to the average of the two components' brightnesses.^[1]^: 4.4 This model is often demonstrated with a Newton disc, where a wheel comprising several color wedges along the circumference is rotated at high speed, such that the human eye cannot temporally differentiate the colors, and they combine to a color with the average brightness (weighted to the angle each color takes up). Another physical model mimics pointillism or halftone printing, where the spatial acuity of the human eye is not sufficient to spatially differentiate the colors, and they combine to a mixture with the average brightness.^[1]^: 4.4 There are no common color models that explicitly use the average model, though many additive or subtractive models can be described in part by the average model.

Pigment mixing

In the practical mixing of pigments, the subtractive model is usually not closely followed. How the pigment mixing behaves depends strongly on the opacity of the pigments.^[1]^: 6.1 Ideally transparent pigments transmit and absorb light, but do not reflect or scatter it and mix according to the subtractive model. Ideally opaque pigments reflect or absorb light, but do not transmit it and mix according to the average model. Most real paints reflect, transmit and scatter light, so mix according to a hybrid between the subtractive and average models.^[1]^: 6.1 Paint color mixing is also affected by the media used as wetting, deagglomeration, and dispersing agents for the pigments. These agents all have their own transparency/opacity and color properties and can also alter the transparency and color of pigments.^{[ citation needed ]}

For example, mixing red and yellow can result in a shade of orange, generally with a lower chroma or reduced saturation than at least one of the component colors. In some combinations, a mix of blue and yellow paint produces green. This occurs when there is sufficient transparency in the pigments, allowing light to penetrate into the mixed paint, where the two colors together absorb light except wavelengths in the green range. Alternately, if the pigments are highly opaque, a combination of blue and yellow paint appears more grayish. In this case, pigment particles simply reflect whatever light hits the outer paint surface, where both blue and yellow light gets reflected and averaged together.

Halftone printing uses non-opaque inks, such that the light transmits once through the ink, reflects off the white substrate (e.g. paper) and transmits a second time through the ink. Increasing the ink printed on the page decreases the brightness of light, and halftone printing follows the subtractive model well.

Related Research Articles

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.

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.

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).

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. The most common colour mixing models are the additive primary colours and the subtractive primary colours.

<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.

The Natural Color System (NCS) is a proprietary perceptual color model. It is based on the color opponency hypothesis of color vision, first proposed by German physiologist Ewald Hering. The current version of the NCS was developed by the Swedish Colour Centre Foundation, from 1964 onwards. The research team consisted of Anders Hård, Lars Sivik and Gunnar Tonnquist, who in 1997 received the AIC Judd award for their work. The system is based entirely on the phenomenology of human perception and not on color mixing. It is illustrated by a color atlas, marketed by NCS Colour AB in Stockholm.

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.

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".

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">Subtractive color</span> Light passing through successive filters

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.

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.

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.

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."

A color space is a specific organization of colors. In combination with color profiling supported by various physical devices, it supports reproducible representations of color – whether such representation entails an analog or a digital representation. A color space may be arbitrary, i.e. with physically realized colors assigned to a set of physical color swatches with corresponding assigned color names, or structured with mathematical rigor. A "color space" is a useful conceptual tool for understanding the color capabilities of a particular device or digital file. When trying to reproduce color on another device, color spaces can show whether shadow/highlight detail and color saturation can be retained, and by how much either will be compromised.

The color cyan, a greenish-blue, has notable tints and shades. It is one of the subtractive primary colors along with magenta, and yellow.

References

1 2 3 4 5 6 7 8 9 10 11 12 Briggs, David. "The Dimensions of Colour" . Retrieved 2 January 2024.

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[BRIGGS-1] 1 2 3 4 5 6 7 8 9 10 11 12 Briggs, David. "The Dimensions of Colour" . Retrieved 2 January 2024.

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