Gamut

The gamut , or gamut of color is a certain complete subset of Couleur S. the most frequent use refers to a subset which, in certain circumstances, precisely represents the extent of the Espace of color that a certain type of material makes it possible to reproduce.

The term is an English word resulting from the medieval musical vocabulary: the notes were noted by letters (and are it always in the notation anglosaxone, to see Cycle of the seven notes ), then were noted by names in the Italian notation; the Greek letter gamma (Γ) indicated the the most serious ground , and C the acutest C. “Gamma-C” was thus the extent of the playable notes, which gave “gamut”.

The gamut of a Moniteur of computer, resulting from a additive Synthèse of the colors red, green, blue, is different from the gamut of a printer, resulting from a subtractive Synthèse, which explains why there are differences between a posted image and the same printed image.

There exist however methods of calibration making it possible to make coincide the gamut screen with that of the printer, using profiles ICC. These methods consist in limiting the gamut used to the intersection between the gamut of the printer and that of the screen, thus avoiding having with the screen of the colors which could not be printed on the printer configured in the profile. The colors called “nonprintable” are converted with the color nearest printable.

It should be noted that aujourd' today the gamuts of the systems of impressions are higher than those of unquestionable screen CRT or LCD, which does not want to say that these printers recover all the gamut screen.

The best printers amateur or professional use several basic colors to recompose the initial image, that makes it possible to extend the gamut. However that does not solve all the problems. Six colors, even more, are used on these printers. The additional colors are generally nuances désaturées towards the white of the subtractive primary Couleurs. For example, in addition to the 4 colors cyan, magenta, yellow and black, for 6 colors one adds a clear cyan and a clear magenta, for 7 colors one adds a gray, etc That makes it possible to extend the gamut but does not allow to solve the problems involved in the system of subtractive recombining.

Two mixed colors are increasingly darker than the starting colors, and if the white of paper is used, one clears up, but loses in saturation. Moreover paper itself is never of a pure white and thus acts on the colors which are deposited above, weakening the saturation and the purity of the pigments.

On the machines offset, it is possible to use various colors other than the subtractive primary colors used in the ink jet printers of ink. That makes it possible to still more extend the gamut during the impression. One can announce the hexachromy, suggested by the system Pantone™ which introduces two additional inks, the orange pure and the pure green allowing to multiply by two the extent of the gamut.

See too

Related articles

External bonds

  • Gamut of some printers with sublimation

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