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Encyclopedia > Gamut

In color reproduction, including computer graphics and photography, the gamut, or color gamut (pronounced /ˈgæmət/), is a certain complete subset of colors. The most common usage refers to the subset of colors which can be accurately represented in a given circumstance, such as within a given color space or by a certain output device. Another sense, less frequently used but not less correct, refers to the complete set of colors found within an image at a given time. In this context, digitizing a photograph, converting a digitized image to a different color space, or outputting it to a given medium using a certain output device generally alters its gamut, in the sense that some of the colors in the original are lost in the process. Computer graphics is a sub-field of computer science and is concerned with digitally synthesizing and manipulating visual content. ... Photography [fÓ™tÉ‘grÓ™fi:],[foÊŠtÉ‘grÓ™fi:] is the process of recording pictures by means of capturing light on a light-sensitive medium, such as a film or sensor. ... Color is an important part of the visual arts. ... A comparison of different color spaces. ... An output device is a piece of hardware which a machine, typically a computer, uses to present information to the user. ...

Contents

Introduction

The term gamut was adopted from the music field, where it meant the set of pitches of which musical melodies were composed; Shakespeare's use of the term in The Taming of the Shrew is sometimes attributed to another author/musician, Thomas Morley[1]. In the 1850s, the term was being applied to a range of colors or hue, for example by Thomas De Quincey who wrote, "Porphyry, I have heard, runs through as large a gamut of hues as marble."[2] Shakespeare redirects here. ... Thomas Morley (1557 or 1558 – October 1602) was an English composer, theorist, editor and organist of the Renaissance, and the foremost member of the English Madrigal School. ...


In color theory, the gamut of a device or process is that portion of the color space that can be represented, or reproduced. Generally, the color gamut is specified in the huesaturation plane, as many systems can produce colors with a wide range intensity within their color gamut; in addition, for subtractive color systems, such as printing, the range of intensity available in the system is for the most part meaningless outside the context of its illumination. In the arts of painting, graphic design, and photography, color theory is a body of practical guidance to color mixing and the visual impact of specific color combinations. ... A comparison of different color spaces. ... An image with the hues cyclically shifted The hues in the image of this Painted Bunting are cyclically rotated with time. ... It has been suggested that this article or section be merged with Chromaticity. ... Intensity is a widely-used term, which can mean: In colloquial use: Strength Amplitude Level In physics: Intensity, power per unit area (W/m2) Field strength of electric, magnetic, or electromagnetic fields. ... For other articles which might have the same name, see Print (disambiguation). ... For the book by Sir Isaac Newton, see Opticks. ...


When certain colors cannot be displayed within a particular color model, those colors are said to be out of gamut. For example, pure red which is contained in the RGB color model gamut is out of gamut in the CMYK model. Red is any of a number of similar colors evoked by light consisting predominantly of the longest wavelengths of light discernible by the human eye, in the wavelength range of roughly 625–750 nm. ... The RGB color model utilizes the additive model in which red, green, and blue light are combined in various ways to create other colors. ... Cyan, magenta, yellow, and key (black) CMYK (or sometimes YMCK) is a subtractive color model used in color printing. ...


A device which is able to reproduce the entire visible color space is somewhat of a holy grail in the engineering of color displays and printing processes. While modern techniques allow increasingly good approximations, the complexity of these systems often makes them impractical. What is "good enough" is dictated by the limitations of human perception. Engineering is the design, analysis, and/or construction of works for practical purposes. ... Nixie tubes, LED-display and VF-display A display device, also known as an information display is a device for visual or tactile presentation of images (including text) acquired, stored, or transmitted in various forms. ... In psychology and the cognitive sciences, perception is the process of acquiring, interpreting, selecting, and organizing sensory information. ...


While processing a digital image, the most convenient color model used is the RGB model. Printing the image requires transforming the image from the original RGB color space to the printer's CMYK color space. During this process, the colors from the RGB which are out of gamut must be somehow converted to approximate values within the CMYK space gamut. Simply trimming only the colors which are out of gamut to the closest colors in the destination space would burn the image. There are several algorithms approximating this transformation, but none of them can be truly perfect, since those colors are simply out of the target device's capabilities. This is why identifying the colors in an image which are out of gamut in the target color space as soon as possible during processing is critical for the quality of the final product. An image is said to be burned when its original gamut considerably exceeds it target gamut, or when the result of processing considerably exceeds the images gamut. ...


Representation of gamuts

A typical CRT gamut.
The grayed-out horseshoe shape is the entire range of possible chromaticities. The colored triangle is the gamut available to a typical computer monitor; it does not cover the entire space. The corners of the triangle are the primaries for this gamut; in the case of a CRT, they depend on the colors of the phosphors of the monitor. At each point, the brightest possible RGB color of that chromaticity is displayed, resulting in the bright Mach band stripes corresponding to the edges of the RGB color cube.

Gamuts are commonly represented as areas in the CIE 1931 chromaticity diagram as shown at right, with the curved edge representing the monochromatic colors. Gamut areas typically have triangular shapes because most color reproduction is done with three primaries. Image File history File links CIExy1931_srgb_gamut. ... Image File history File links CIExy1931_srgb_gamut. ... Chromaticity is the quality of a color as determined by its purity and dominant wavelength. ... A Mach band is an optical illusion, named after Ernst Mach. ... In the study of the perception of color, one of the first mathematically defined color spaces was the CIE XYZ color space (also known as CIE 1931 color space), created by the International Commission on Illumination (CIE) in 1931. ... Something which is monochromatic has a single color. ...


However, the accessible gamut depends on the brightness; a full gamut must therefore be represented in 3D space, as below:

The pictures at left show the gamuts of RGB color space (top), such as on computer monitors, and of reflective colors in nature (bottom). The cone drawn in grey corresponds roughly to the CIE diagram at right, with the added dimension of brightness. 3D gamut diagram for RGB colors See also the source code:media:gamut. ... 3D gamut diagram for natures colors See also: File links The following pages link to this file: Gamut Image:Gamut. ...


The axes in these diagrams are the responses of the short-wavelength, middle-wavelength, and long-wavelength cones in the human eye. The other letters indicate black, red, green, blue, cyan, magenta, yellow, and white colors. (Note: These pictures are not exactly to scale.) // A human eye. ...


The left diagram shows that the shape of the RGB gamut is a triangle between red, green, and blue at lower luminosities; a triangle between cyan, magenta, and yellow at higher luminosities, and a single white point at maximum luminosity. The exact positions of the apexes depends on the emission spectra of the phosphors in the computer monitor, and on the ratio between the maximum luminosities of the three phosphors (i.e., the color balance). Green screen A phosphor is a substance that exhibits the phenomenon of phosphorescence (sustained glowing after exposure to light or energised particles such as electrons). ...


The gamut of the CMYK color space is, ideally, approximately the same as that for RGB, with slightly different apexes, depending on both the exact properties of the dyes and the light source. In practice, due to the way raster-printed colors interact with each other and the paper and due to their non-ideal absorption spectra, the gamut is smaller and has rounded corners.


The gamut of reflective colors in nature has a similar, though more rounded, shape. An object that reflects only a narrow band of wavelengths will have a color close to the edge of the CIE diagram, but it will have a very low luminosity at the same time. At higher luminosities, the accessible area in the CIE diagram becomes smaller and smaller, up to a single point of white, where all wavelengths are reflected exactly 100 per cent. The exact coordinates of white are of course determined by the color of the light source.


Limitations of color representation

The color gamut of most systems can be understood as a result of difficulties producing pure monochromatic (single wavelength) light. The best technological source of (nearly) monochromatic light is the laser, which is expensive and impractical for many systems (as laser technology improves and becomes more inexpensive, this may no longer be the case). Other than lasers, most systems represent highly saturated colors with a more or less crude approximation, which includes light with a range of wavelengths besides the desired color. This may be more pronounced for some hues than others. Something which is monochromatic has a single color. ... The wavelength is the distance between repeating units of a wave pattern. ... Experiment with a laser (likely an argon type) (US Military) In physics, a laser is a device that emits light through a specific mechanism for which the term laser is an acronym: light amplification by stimulated emission of radiation. ...


Systems which use additive color processes usually have a color gamut which is roughly a convex polygon in the hue-saturation plane. The vertices of the polygon are the most saturated colors the system can produce. In subtractive color systems, the color gamut is more often an irregular region. A convex pentagon In geometry, a convex polygon is a simple polygon whose interior is a convex set. ...


Comparison of various systems

Following is a list of representative color systems more or less ordered from large to small color gamut:

  • Laser video projector uses 3 lasers to produce the broadest gamut available in practical display equipment today, derived from the fact that lasers produce truly monochromatic primaries. The systems work either by scanning the entire picture a dot at a time and modulating the laser directly at high frequency, much like the electron beams in a CRT, or by optically spreading and then modulating the laser and scanning a line at a time, the line itself being modulated in much the same way as in a DLP.
  • Photographic film can reproduce a larger color gamut than typical television, computer, or home video systems.[3]
  • Laser light shows use lasers to produce very nearly monochromatic light, allowing colors far more saturated than those produced by other systems. However, mixing hues to produce less saturated colors is difficult. In addition, such systems are complex, expensive, and ill-suited to general video display.
  • CRT and similar video displays have a roughly triangular color gamut which covers a significant portion of the visible color space. In CRTs, the limitations are due to the phosphors in the screen which produce red, green, and blue light.
  • Liquid crystal display (LCD) screens filter the light emitted by a backlight. The gamut of an LCD screen is therefore limited to the emitted spectrum of the backlight. Typical LCD screens use fluorescent bulbs for backlights. LCD Screens with certain LED backlights yield a more comprehensive gamut than CRTs.
  • Television uses a CRT display (usually), but does not take full advantage of its color display properties, due to the limitations of broadcasting. HDTV is far better, but still somewhat less than, for example, computer displays using the same display technology.
  • Paint mixing, both artistic and for commercial applications, achieves a reasonably large color gamut by starting with a larger palette than the red, green, and blue of CRTs or cyan, magenta, and yellow of printing. Paint may reproduce some highly saturated colors that can not be reproduced well by CRTs (particularly violet), but overall the color gamut is smaller.
  • Printing typically uses the CMYK color space (cyan, magenta, yellow, and black). A very few printing processes do not include black; however, those processes (with the exception of dye-sublimation printers) are poor at representing low saturation, low intensity colors. Efforts have been made to expand the gamut of the printing process by adding inks of non-primary colors; these are typically orange and green (see Hexachrome) or light cyan and light magenta. Spot color inks of a very specific color are also sometimes used.
  • A monochrome display's color gamut is a one-dimensional curve in color space.

A laser video projector takes a video signal and modulates a laser beam in order to project a raster-based image. ... CRT can mean: Cathode Ray Tube, in electronics, a display device (such as those used in one type of television) C Run-Time, in computing Charitable Remainder Trust, in Law Chinese Remainder Theorem, in mathematics Corneal Refractive Therapy, in medicine Criterion-referenced test, in U.S. schools Critical race theory... The DLP Logo Digital Light Processing (DLP) is a technology used in projectors and video projectors. ... This article or section does not cite its references or sources. ... The home video business rents and sells videocassettes and DVDs to the public. ... Copper Bromide laser in operation. ... Cathode ray tube employing electromagnetic focus and deflection Cutaway rendering of a color CRT Electron guns Electron beams Focusing coils Deflection coils Anode connection Mask for separating beams for red, green, and blue part of displayed image Phosphor layer with red, green, and blue zones Close-up of the phosphor... Reflective twisted nematic liquid crystal display. ... Backlights are lights that are attached to LCD displays so that they can be seen at night. ... Blue, green and red LEDs. ... Broadcasting is the distribution of audio and/or video signals which transmit programs to an audience. ... Projection screen in a home theater, displaying a high-definition television image. ... This article does not cite its references or sources. ... For other articles which might have the same name, see Print (disambiguation). ... Cyan, magenta, yellow, and key (black) CMYK (or sometimes YMCK) is a subtractive color model used in color printing. ... HIII Samsung SPP-2040 working. ... Hexachrome is Pantones six-color printing process. ... // Definition of Spot Color In offset printing, a spot color is any color generated by an ink (pure or mixed) that is printed using a single run. ... A photograph of a sign in grayscale The same photograph in black and white Monochrome comes from the two Greek words mono (μωνο, meaning one), and chroma (χρωμα, meaning surface or the color of the skin). A monochromatic object has a single color. ...

References

  1. ^ John H. Long (Jan. 1950). Shakespeare and Thomas Morley.
  2. ^ Thomas De Quincey (1854). De Quincey's works. James R. Osgood. 
  3. ^ Film gamut, apples, and oranges. Retrieved on 26 April 2007.

External links


  Results from FactBites:
 
Gamut - Wikipedia, the free encyclopedia (1680 words)
The left diagram shows that the shape of the RGB gamut is a triangle between red, green, and blue at lower luminosities; a triangle between cyan, magenta, and yellow at higher luminosities, and a single white point at maximum luminosity.
The gamut of the CMYK color space is, ideally, approximately the same as that for RGB, with slightly different apexes, depending on both the exact properties of the dyes and the light source.
The gamut of an LCD screen is therefore limited to the emitted spectrum of the backlight.
Gamut - LoveToKnow 1911 (278 words)
GAMUT (from the Greek letter gamma, used as a musical symbol, and ut, the first syllable of the medieval hymn Sanctus Johannes), a term in music used to mean generally the whole compass or range of notes possessed by an instrument or voice.
Historically, however, the sense has developed from its stricter musical meaning of a scale (the recognized musical scale of any period), originating in the medieval "great scale," of which the invention has usually been ascribed to Guido of Arezzo in the 11th century.
The whole question is somewhat obscure, but, in the evolution of musical notation out of the classical alphabetical system, the invention of the medieval gamut is more properly assigned to Hucbald (d.
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