Additive color

Last updated

Red, green, and blue lights combining by reflecting from a white wall: secondary colors yellow, cyan, and magenta are found at the intersections of red and green, green and blue, and blue and red. The intersection of all three primary colors together yields white. RGB combination on wall.png
Red, green, and blue lights combining by reflecting from a white wall: secondary colors yellow, cyan, and magenta are found at the intersections of red and green, green and blue, and blue and red. The intersection of all three primary colors together yields white.
James Clerk Maxwell, with his color top that he used for investigation of color vision and additive color J C Maxwell with top.jpg
James Clerk Maxwell, with his color top that he used for investigation of color vision and additive color

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. [1] Modern formulations of Grassmann's laws [2] 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 gray or black background.

Contents

Additive color models are applied in the design and testing of electronic displays that are used to render realistic images containing diverse sets of color using phosphors that emit light of a limited set of primary colors. 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 light-emitting phosphors which appear as a variety of single colors when viewed from a normal distance.

Additive color, alone, does not predict the appearance of mixtures of printed color inks, dye layers in color photographs on film, or paint mixtures. Instead, subtractive color is used to model the appearance of pigments or dyes, such as those in paints, inks.

The combination of two of the common three additive primary colors in equal proportions produces an additive secondary color—cyan, magenta or yellow. Additive color is also used to predict colors from overlapping projected colored lights often used in theatrical lighting for plays, concerts, circus shows, and night clubs. [3]

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, a gamut is a plane convex polygon with corners at the primaries. For three primaries, it is a triangle.

History

The first permanent color photograph, taken by Thomas Sutton, under the direction of James Clerk Maxwell in 1861 Tartan Ribbon.jpg
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. [4] 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. [5]

See also

Additive color mixing with CD covers

Related Research Articles

<span class="mw-page-title-main">Color</span> Visual perception of the light spectrum

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">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

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 color mixing models are the additive primary colors and the subtractive primary colors.

<span class="mw-page-title-main">RGB color spaces</span> Any additive color space based on the RGB color model

An RGB color space is one of many specific additive colorimetric color spaces based on the RGB color model.

<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">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.

An RG color model is a dichromatic color model represented by red and green primary colors. These can only reproduce a fraction of the colors possible with a trichromatic color space, such as for human color vision.

<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.

<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">Color triangle</span> Arrangement of colors within a triangle

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

<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">Color space</span> Standard that defines a specific range of colors

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.

<span class="mw-page-title-main">Impossible color</span> Color that cannot be perceived under ordinary viewing conditions

Impossible colors are colors that do not appear in ordinary visual functioning. Different color theories suggest different hypothetical colors that humans are incapable of perceiving for one reason or another, and fictional colors are routinely created in popular culture. While some such colors have no basis in reality, phenomena such as cone cell fatigue enable colors to be perceived in certain circumstances that would not be otherwise.

<span class="mw-page-title-main">Paint mixing</span>

Paint mixing is the practice of mixing components or colors of paint to combine them into a working material and achieve a desired hue. The components that go into paint mixing depend on the function of the product sought to be produced. For example, a painter of portraits or scenery on a canvas may be seeking delicate hues and subtle gradiations, while the painter of a house may be more concerned with durability and consistency of colors in paints presented to customers, and the painter of a bridge or a ship may have the weatherability of the paint as their primary concern.

References

  1. ↑ MacEvoy, Bruce. "handprint : colormaking attributes". www.handprint.com. Retrieved February 26, 2019.
  2. ↑ MacEvoy, Bruce. "handprint : colormaking attributes". www.handprint.com. Retrieved February 26, 2019.
  3. ↑ David Briggs (2007). "The Dimensions of Color". Archived from the original on September 28, 2015. Retrieved November 23, 2011.
  4. ↑ "James Clerk Maxwell". Inventor's Hall of Fame, Rochester Institute of Technology Center for Imaging Science. Archived from the original on September 18, 2010.
  5. ↑ Robert Hirsch (2004). Exploring Colour Photography: A Complete Guide. Laurence King Publishing. ISBN   1-85669-420-8. Archived from the original on February 25, 2017.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.