color

There are established models of color, each discipline uses it own

method for describing and discussing color intelligently.

Color modes

• Index

• Grayscale

• Duotone

• Rgb

• Lab

• Cmyk

Indexed color mode

• An image in Indexed color mode has one channel and a color table containing a maximum of 256 colors or shades (8-bit color). This is the maximum number of colors available in such web-friendly formats such as gif and png-8.

Duotone

• Is a printing method in which two or more plates are used to add richness and tonal depth to a grayscale image.

L A B color

• Is a three-channel mode that was developed for the purpose of achieving consistency among various devices, such as printers and monitors. The channels represent lightness, the colors green to red, and the colors blue to yellow. Photo CD images can be converted to lab color mode or rgb color mode in photoshop. Sometimes files are saved in lab color mode for export to other operating systems….

HSB

Based on the human perception of color, the HSB model describes three fundamental characteristics of color: .Hue is the color reflected from or transmitted through an object. It is measured as a location on the standard color wheel, expressed as a degree between 00 and 360°0 In common use, hue is c identified by the name of the color such as red, orange, or green. .Saturation, sometimes called chroma, is the strength or purity of the color. Saturation represents the amount of gray in proportion to the hue, measured as a percentage from 0% (gray) to 100% (fully saturated). On the standard color wheel, saturation increases from the center to the edge. .Brightness is the relative lightness or darkness of the color, usually measured as a percentage from 0% (black) to 100% (white).

A l arge percentage of the visible spectrum can be represented by mixing red, green, and blue (RGB) colored light in various proportions and intensities. Where the colors overlap, they create cyan, magenta, and yellow.

RGB

Because the RGB colors combine to create white, they are also called additive colors. Adding all colors together creates white-that is, all light is reflected back to the eye. Additive colors are used for lighting, video, and monitors. Your monitor, for example, creates color by emitting light through red, green, and blue phosphors.

In theory, pure cyan (C), magenta (M), and yellow (Y) pigments should combine to absorb all color and produce black; for this reason they are also called subtractive colors. Because all printing inks contain some impurities, these three inks actually produce a muddy brown and must be combined with black (K) ink to produce a true black. (The letter K is used to avoid confusion, because B also stands for blue.) Combining these inks to reproduce color is called four-color process printing

CMYK

Grayscale uses shades of gray to represent an object. In Adobe Illustrator, every grayscale object has a brightness value ranging from 0% (white ) to 100% (black). Images produced using black-and- white or grayscale scanners are typically displayed in grayscale. Grayscale also lets you convert color artwork to high-quality black-and-white artwork. In this case, Adobe Illustrator discards all color information in the original artwork; the gray levels (shades) of the converted objects represent the luminosity of the original objects. When you convert grayscale objects to RGB, the color values for each object are assigned that object's previous gray value. You can also convert a grayscale object to a CMYK object.

Grayscale

The gamut of a color system is the range of colors that can be displayed or printed. The spectrum of colors that can be viewed by the human eye is wide( than any method of reproducing color. Among the color models used in Adobe Illustrator, RGB has the largest gamut. The RGB gamut contains the subset of colors that can be viewed on a computer or television monitor {which emits red, green, and blue light). Some colors, such as pure cyan or pure yellow, can't be displayed accurately on a monitor. The smallest gamut is that of the CMYK model, which consists of colors that can be printed using process-color inks. When colors that cannot be printed are displayed on the screen, they are referred to as out-of-gamut colors {that is, they are outside the CMYK gamut).

Color Gamut

Process colors,Spot colors, and Registration color

Working with process colors, spot colors, and registration color, It is important to understand the different types of color used in graphics -global process color, non-global process color, spot color, and registration color-since the color type determines how colors are updated throughout the document, and how they are separated and printed.

Global process color Process colors are the four inks used in traditional color separations: cyan, magenta, yellow, and black. In Illustrator, all four color models that result in color separations when printed-that is, CMYK, RGB, HSB, and Grayscale-are referred to as process colors. Global process colors are those that automatically update throughout the document when the swatch is edited, that is, every object containing the color changes when the swatch is modified.

Global process color

Non-global process colors also can be assigned any of the four color models (CMYK, RGB, HSB, and Grayscale), but do not automatically update throughout the document when the color is edited. Process colors are non-global by default; a non-global process color can be changed to a global process color using the Swatch Options dialog box.

Non-global process color

Spot colors are special premixed colors that are used instead of, or in addition to, CMYK inks, and that require their own separations and their own plates on a printing press. When a spot color swatch is edited, the color is updated globally throughout the document. You can assign any of the four color models to a spot color. Spot colors mayor may not fall within the CMYK gamut; for example, a spot color may be a neon or metallic ink that is not within the CMYK gamut, or it may be a shade of green that falls within the gamut.

Spot colors

A registration color is applied to objects that you want to print on all plates in the printing process, including any spot color plates. Registration color is typically used for crop marks and trim marks..

Registration color