The use of color on digital print applications has become so widespread that people have come to expect color on most printed pieces. More often than not, color is included on items as commonplace as bills and statements. The widespread use of color on printed pieces is a direct result of the superior quality and the ease of application of color due to the ever-improving technology of digital printing. This increased use is also due to the continuous reduction in cost for applying color to digitally printed documents. The use of color for applications such as brochures, newsletters, product offers, direct mail pieces, or even a simple monthly statement, provides a means for organizations to distinguish themselves from their competitors.

Many experts agree that the use of color for even the most basic document helps the consumer retain information more readily than if the information was offered simply in black and white. Color can also highlight specific bits of data that not only reinforces the information, but also helps the consumer gain a better understanding of the entire message being presented. Color increases the response rate of direct mail pieces, captures attention more effectively, and provides documents with an appealing, professional appearance.

The color gamut refers to the range of colors that can be viewed, displayed, or printed. Digital printing equipment is able to reproduce a greater range of color than traditional offset technology which gives it a distinct advantage over offset.

The items in the list below are arranged from the greatest to the least in terms of the range of colors that each is able to reproduce:

1. Human Eye

2. Photographic Film

3. Television or Computer Monitor

4. Digital Printing Equipment

5. Offset Printing

The following are the properties that are used to define color:

• Hue: describes the name of a color such as red, orange, violet, or blue.
  
  
• Value: describes the lightness or darkness of the color. Value is also known as tone, tone value, or lightness.
  
  
• Saturation: describes the intensity of the color such as bright or dull. Saturation is also known as intensity or chroma. It is important to remember that a color that has a very intense or bright level of saturation may not necessarily be very light in value just as a very dull color may not necessarily be very dark in tone or value.

Additive Color

Color reproduction on the computer monitor (and on television) is achieved by combining Red, Green, and Blue light (RGB) in varying levels to produce a full color image. Red, green, and blue are the primary colors of white light and they cannot be produced by the combination of any other colors. When they are combined full strength, they will produce white light. This process is known as the Additive Color Process, because when the colors of light are added to one another the result is an increase in light intensity. An object appears to be white when all portions of the white light illuminating the object are reflected back to the eye. If none of the additive primaries are present, the color is perceived as black.

When two primary colors of light are combined, a secondary color is produced. These secondary colors of light are Cyan, Magenta, and Yellow (CMY). The secondary light colors are also the primary colors of the Subtractive Color Process. This process forms the basis for the use of pigments that are used to reproduce color for printed media.

The combination of 100% of any two primary colors of light will result in a secondary color. 100% green light and 100% blue light result in cyan; 100% blue light and 100% red light result in magenta; and 100% red light and 100% green light result in yellow.

Subtractive Color

Red, Green and Blue (RGB), are the primary colors of white light and are called the Additive Primary Colors. We are able to see color because different objects reflect and absorb, or subtract, the primary colors of light differently. For example, we see an object as yellow because it absorbs (or subtracts) blue light from white light. Since the blue light has been absorbed, the red light and green light are leftover and are reflected back to our eyes. Red light and green light combine to make yellow and so we see the color of the object as yellow. This is known as the Subtractive Color Process because portions of the visible light spectrum are subtracted from white light to reveal color. If 100% of the red light is subtracted from white light the resulting color is cyan. (The green light and blue light are the remaining primary light colors after the red is removed and the green and blue combine to form cyan). If 100% of the green light is subtracted from white light the result is magenta (red light and blue light form magenta) and when 100% of the blue light is subtracted from white light the result is yellow (red light and green light form yellow). Cyan, Magenta, and Yellow (CMY) are the Subtractive Primary Colors, and are the primary colors used for creating pigments for color reproduction in process color printing.

The combination of the subtractive primary color pigments in varying degrees is what creates the illusion of a full-color printed image. In the lightest and whitest areas of the printed image, very little of the primary colors are present so these areas appear very light. In the darkest areas of the printed image, much more of each color is present making the areas appear darker. The combination of the three subtractive primaries, each at 100% strength, should create black, but since cyan, magenta, and yellow color pigments are not perfect, there is no way of creating a true black color when they are combined. If full strength cyan, magenta, and yellow, are combined, the resulting color is actually a dark, muddy brown. Even if it were possible to combine all three primaries at full strength to create black, printing 100% of any or all of the subtractive primaries can cause such an extreme saturation of color on the printed surface that it can result in very poor print quality. Because of this problem, the addition of black is necessary to assist the cyan, magenta, and yellow in creating the darkest hues, deepening shadows, and producing a true black text.

Cyan, Magenta, Yellow, and Black, (CMYK), form the basis of the four-color printing process. The "K" is used to signify black to avoid confusion with blue.

Color Neutralization

Strong highlight areas (pure white) and strong shadow areas (pure black) should be neutralized with scanning software or in PhotoShop. Pure white, which is 100% red, 100% green, and 100% blue, and represented as the value R255, G255, B255, can be backed off to R247, G247, and B247. Pure black, which is 0% red, 0% green, and 0% blue, and represented as the value R0, G0, B0, can be advanced to R5, G5, and B5. Software programs will convert the RGB values into the correct CMYK values for output. Color neutralization will provide more pleasing highlights and shadows as well as a better gray balance for the entire image.

Dot Size

In order to achieve the best results, it is important to know the minimum and maximum dot areas that can be reproduced by the digital equipment. With offset printing, dot sizes between 5% and 95% can be accurately printed and with digital equipment the range is usually between 3% and 97%.

Color Management Systems (CMS)

Color Management systems provide a profile of the color characteristics for each device used in the print workflow, such as a scanner or a digital press. Color characteristics profiles are incorporated into the print workflow in order to provide consistent color reproduction throughout the process. Popular color management systems include Apple ColorSync and Microsoft ICM.

Cielab

Cielab is an acronym for "Commission Internationale de l'Eclairage Lab," with "L" representing lightness, "a" representing the re/green axis, and "b" representing the blue/yellow axis. Cielab is the worldwide standard for color measurement and allows for easy communication concerning colors because it is based on numerical values, which takes the guess work out of color correction.

Cielab models are used for verifying whether the colors of an image fall within the color range of the print process and the piece of equipment that will be used to output the image. Cielab is also used to check the color-carrying capabilities of various papers, which is beneficial for clients in determining the types of papers that are best suited for their application. As most printers are aware, coated stock is capable of displaying a wider color gamut than uncoated paper, so using Cielab to illustrate the color gamut of various papers can justify the use of a more costly stock to achieve better results.

Color Matching

Sometimes it may be impossible to match a spot color exactly. All color digital presses can print four-color process, but not all models can be configured to print any additional colors when spot colors are needed. Most of the time, spot colors are converted to their equivalent values in CMYK in order for the spot color to be simulated with the process colors. The results may vary widely depending on which color is being simulated. It is helpful to have a swatchbook, such as the "Solid-to-Process" swatchbook offered by PANTONE, which shows the solid colors that can best be reproduced using process colors.

Coverage

When using digital equipment, the maximum coverage of the toner or ink on the substrate must be limited. The combination of all the process colors (Cyan, Yellow, Magenta, and Black) at full strength would be 400% coverage (100% for each process color) resulting in an oversaturation of toner, creating a thick muddy appearance on the substrate. The combination of the process colors into various quantities should not exceed a total of 320% to prevent oversaturation from occurring.