Glossary of Terms

Additive Primaries: The colors red, green, and blue. When white light is broken down into its component parts, a rainbow (visible spectrum) is created. Dividing the rainbow into about equal thirds results in red light, green light, and blue light. By combining (adding) the three colors of light together, white light is created.

Against the Grain: The direction across the grain. Paper is used at right angles to its grain in a sheetfed press. Paper is less strong and more apt to change size against the grain.

Banding: A printing defect characterized by light or dark lines in an image in the direction of the printing. In the case of inkjet imaging it is caused by a jet or printhead that is not properly aligned, inoperative, or incorrectly indexed. The chemistry of the substrate surface can also contribute to banding.

Bitmap: A series of individual dots or pixels that define graphics. On a color or black-and-white system, a bitmap defines a character or an image by turning each pixel on or off. Each pixel must be recorded for a full image. Paint programs use this format and are different than vector graphics, which define graphics by points.

Brightness: 1. The amount of light being reflected from a surface. 2. In a printed reproduction, the lightness value regardless of the hue or saturation. Brightness is affected by the reflectance of the paper. This is not called brilliance.

CIE Color Space: a three dimensional mapping system that is used to locate or plot the three color attributes of lightness or darkness, red-green, or blue-yellow values.

Cockle: To wrinkle or pucker. Paper cockles or buckles permanently when too much liquid is applied. Frequently occurs when a volume of water-based ink is applied in a small area.

Color: The visual sensation of human response to seeing certain wavelengths of light. To see color, there must be a light source illuminating objects that absorb or reflect the light to the human eye. The color or colors seen depend on the quality of the light source, the objects light absorbability or reflectivity (the color of the object), and the sensitivity of the human eye.

Color Balance: Maintaining the ration of cyan, magenta, and yellow ink during printing. This will keep all color hues consistent and produce a picture with the desired color, one without an unwanted color cast or color bias.

Color Gamut: The complete range of hues and strengths of colors that can be achieved with a given set of colorants such as cyan, magenta, yellow, and black inks on a specific substrate.

Colorimeter: An instrument for measuring the tristimulus values of color with a precise and defined response that is similar to the human eye.

Color Matching System: 1. A color chart that has been printed or stored in an electronic system and is used to compare color samples, also called a color swatching system. 2. A computer-based process that can measure a color and formulate a new set of colorant amounts to reproduce the measured color. The system can be used to mix special color inks.

Color Separation: The process of making a separate electronic or photographic record of the amounts or each process color of cyan, magenta, yellow, or black needed to reproduce an original copy. The record may be a photographic film made through the red, green, and blue separation filters or a computer file. A set of four separations, cyan, magenta, yellow, and black, are required to reproduce an original color image, since each of the four process colors must be represented. The separations may be made photographically using traditional methods or digitally using electronic scanners and computer programs. The original copy may be a transparency (slide), reflection photographic print, drawing, painting, or printed reproduction.

Color Space: A three-dimensional space or model into which the three attributes of a color can be represented, plotted, or recorded. These attributes are usually called hue, value, and chroma.

Cyan: 1. The subtractive primary that appears blue-green and absorbs red light. 2. A blue-green ink that is used as one ink in the four-color printing process, sometimes referred to as process blue.

CYMK: Abbreviation for cyan, yellow, magenta, and black process colors or inks.

Density: The visual darkness of a material caused by its capability to absorb or reflect the light illuminating the material. Density is measured with a densitometer. Colored materials are measured through their complimentary filters. Density differences are sometimes called gray levels. As density increases the amount of reflected or transmitted light is reduced. The amount of light absorbed is inversely proportional to the amount of light reflected from or transmitted through the sample.

Dot: The term used to designate the mark or spot on the paper or substrate.

Dot Gain: The apparent dot size increase from the film to the printed reproduction.

Feathering: The bleeding of the ink into a non-printed area usually due to capillary action of the fibers in the substrate.

Glossy: A shiny surface that reflects the specular component of light away from the eye and, therefore, appears more dense.

Gray Scale: A narrow strip of paper containing an orderly progression in definite steps or patches of gray densities or printed halftone steps ranging in dot sizes from zero to 100%. A gray scale is used to analyze and optimize the contrast of black-and-white and colored reproductions. The gray scale may be reflection-type made on photographic paper, on a color proof, or printed on paper. On film, with definite steps of either continuous tone or halftone dots, it is called a step tablet. On film without definite steps, it is a continuous wedge. On film with dots and definite steps, it is a halftone scale. On a computer monitor, shades of gray are created by varying the intensity of the screen's pixels, rather than by using a combination of only black-and-white pixels to produce shading. Printed, it is produced as a narrow strip of paper, usually in the trim area of a job, and used for analyzing printing characteristics.

Halftone: A negative or positive image made by photographing an image through a screen so that the detail of the image is reproduced with dots. The reproduction simulates the different tones of the original by transforming them into dots of varying sizes arranged in a grid pattern that has a given frequency. For example, a 150 lines per inch halftone would contain 150 rows and 150 columns of dots (22,500 in a square inch) that could vary in size from zero percent to 100 percent, also called screened negative or screened positive. Halftones can also be generated electronically from digital data.

Holdout: The ability of the paper to keep the ink on the surface. The ink gloss is directly related to the paper*s ability to hold the ink on the surface. Too much holdout causes offset.

Hot Melt Ink: The class of inkjet inks that is solid at room temperature and liquid at an elevated temperature. Usually these inks are wax based and provide extremely high color saturation, very sharp edge definition, and independence from the characteristics of the printing substrates. The disadvantage is the ink resides on the surface of the substrate with little penetration unless there is a subsequent treatment. This results in inks that can be chipped or rubbed off the surface.

Hue: The attribute of color that designates its dominant wavelength and distinguishes it from other colors. Red is a different hue than green. While bright red and dark red may have a different brightness or lightness, they may be the same hue.

Imagesetter: A high-resolution laser output device that writes onto photosensitive paper or film bitmap data generated by an RIP.

Impulse inkjet: The branch of inkjet technology where droplets are produced by a rapid pressure pulse created in an ink chamber causing the expulsion of an ink droplet through the orifice plate. In piezo-based impulse inkjet systems this disturbance is caused by a rapid small change in the volume of the ink chamber behind the orifice plate. In thermal impulse technology this disturbance is created by a rapidly growing and collapsing bubble due to ohmic or electrical resistive heating. Sometimes erroneously referred to as drop on demand type of inkjet printing.

Jet: A stream of fluid (ink) produced by discharge through an orifice into free space.

Magenta: 1. The subtractive primary color that appears bluish red and absorbs green light. 2. One ink in the four -color printing process, sometimes referred to as process red.

Mask: A photographic film placed over an image in order to modify the light that will pass through the image, thereby changing a characteristic of the reproduction. This task can also be handled electronically on digital prepress systems. There are a variety of masks, including area masks, outline masks and unsharp masks.

Matte: A dull or rough surface, lacking gloss or luster, such that more light is reflected to the eye and colors appear less dense.

Metameric color: A color that changes its perceived hue under different illumination. For example, it is possible to have two color samples match under tungsten (incandescent) illumination and not match when viewed in sunlight.

Monochrome: One color; refers to black and white printing.

Mottle: Uneven print density or uneven color. A defect in matrix color printing because of a lack of dot placement accuracy or variable dot density. Most readily apparent in areas of solid printing.

Offset: 1. A type of conventional (non-demand type) printing employing a plate cylinder with areas of hydrophobic, (water-repulsive) and hydrophilic (water-compatible) areas. The hydrophobic areas will then attract oil-based printing inks. This image is also transferred to a blanket cylinder, which then contacts the surface to be printed. Also known as lithography. 2. A defect in a printing system where a printed image is transferred onto the back of another printed sheet of paper because the ink is not dried before the second paper contacted it.

Opacity: The property of paper that minimizes the "show-through" of printing from the back side or the next sheet.

Orifice: A hole or aperture without appreciable length. In most cases this is the technically correct term for the hole employed in inkjet printing systems.

Overprint: To print dots of one process color ink over dots of another process color ink to produce overprint colors or secondary colors such as red, green and blue.

Piezo Printing: The type of inkjet printing in which an electrical signal causes a piece of crystal in the printing nozzle to deflect, thereby ejecting the ink droplet from the nozzle.

Pixel: Acronym for picture element, the smallest picture sample that can be sensed, manipulated or output by a digital system. In a color system, each pixel is represented either by cyan, magenta, yellow and black values, or red, green and blue values.

Primary Colors: The colorants of a system that are used to print the colors for the entire reproduction. Cyan, magenta and yellow are subtractive primary colors, while red, green and blue are additive primary colors.

Prime: The act of initially introducing ink to a inkjet printhead and forcing ink out of the orifices to expel air from the chamber or the ink manifold.

Process Color: A printed color or image that is rendered by a combination of three primary colors. In theory, all colors of the spectrum can be reproduced by combining different amounts of three primary colors. The three primary colors in the subtractive system are cyan, magenta, and yellow. Because of paper defects, show through and variations in illuminating light, it is very difficult in practice to have a complete color gamut from the three primaries. Additionally, to make black by combining the three primaries is very expensive because it utilizes so much ink. Therefore, black is frequently added as a fourth ink component. This process is called under-cutting.

Resolution: In matrix printing, the number of dots or picture elements (pixels) per unit length. Frequently, the vertical and horizontal resolution is the same. Expressed as dots per inch in the English system and dots per centimeter in the metric system.

RIP: Abbreviation for raster image processor, a software program or computer that determines what value each pixel of a final output page bitmap should have based on commands from the page description language.

Saturation: the attribute of a color that describes its degree of strength and its departure from a gray with the same lightness.

Sharpen: To make halftone printing dots smaller. Using negative separations, sharpening is accomplished with dot etching. Over exposure will also sharpen the negative films. When positive working plates are made using positive transparencies, sharpening happens automatically and the size of the printing dots are reduced by 5%. This sharpening is called negative dot gain.

Spectrum: The range of colors visible when white light is passed through a prism. The prism divides the white light into wavelengths from short to long.

Spot Color: Localized color assigned to a graphic or block of text, prepared with a color break and printed without the use of color separations. Usually process color is not assigned to the spot color areas. Spot color is frequently printed with non-process color inks, although process inks can be used as well.

Substrate: Any material that can be printed on, such as paper, film, plastic, fabric, cellophane, or steel.

Subtractive Primaries: The process ink colors, cyan, magenta, and yellow. Each absorbs or subtracts its complimentary color, red, green, or blue, from the light reflecting off the paper. Cyan, magenta and yellow printed together produce a three-color black, which is slightly brownish because of the unwanted hue error of the inks.

Tack: The amount of stickiness in printing inks that makes them print while minimizing dot gain.

TIFF: An acronym for Tag Image File Format, a standard file format that was developed by Aldus Corporation for bitmap or raster graphics, usually for scanned images. TIFF can handle a variety of image data, from 8-bit black and white images, to 24-bit color RGB (Red, Green, Blue) or CYMK images. Vector graphics are usually stored in PICT or EPS (Encapsulated PostScript) format.

Tone: The character of a color, its quality or lightness. Used as a verb (to tone) means to change or modify a color.

Trapping: 1. Adjoining colors overlapped by a row or two of halftone dots to minimize the effect of misregister. Without trapping a fine white line would appear between two color images during the printing of process color. 2. The ability of an ink to print onto another ink. One hundred percent trapping occurs when the same amount of ink will print on the first ink as on the unprinted substrate. More frequently undertrapping occurs, because one wet ink will not adhere properly when applied to another wet layer of ink. Ink trapping is controlled by adjusting tack.

White Light: Illumination, such as sunlight, composed of all the colors of light in the visible spectrum. The visible spectrum components can be seen in a rainbow or in sunlight shining through a prism.

WYSIWYG: An acronym for "what you see is what you get." The term is used in several situations, such as when a color proof is shown to the customer. The person presenting the proof assures the customer that what you see is what the press will produce. Or, in desktop publishing, the term is used to refer to the ability of desktop computers to display on their monitors a reasonable representation of what will appear on the printed page.

Yellow: 1. The subtractive primary color that appears yellow and absorbs blue light. 2. One of the four-color process inks made from the organic pigment, diarylide yellow, formerly called benzidine yellow.

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