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D

DCS: Desktop color separation. Used when saving photographs as EPS files. It is simply a document format used in Desktop Publishing.

Decrement: In color process printing, it describes the decrease of a brightness, hue, or saturation value in an image.

Densitometer: In lithography, a reflection densitometer is used to measure the density of the ink colors to determine they are consistent throughout the run. A transmission densitometer can be used to check reproduction dot sizes in order to maintain quality assurance in color. Both measure optical density and are considerably more sensitive and accurate than is the human eye.

Density: A measure of the relative difference between a whit area and a toned or black area. Can be applied both to black and white and color. Or the ability of a material to absorb light. It is inversely proportional to the amount of light reflected or transmitted through a sample.

Descenders: A typographic term for the portion of lowercase characters that falls below the main body of the letter. The lower case g, j, p, q and y have descenders.

Device Independent: A program or file format that can be used with two or more different computing devices and produce identical results. For example, a page saved in Postscript format should be printable on an HP LaserPrinter IV or on a Linotronic output device.

Differential Spacing: In typography, allowing letters to take up varying horizontal space in relation to their widths. For example, the "i" takes up less space than an upper-case "W". Opposite of fixed spacing, where each letter is assigned the same space regardless of its shape or width.

Digitize: To convert an image or signal into binary code. Visual images are digitized by scanning them and assigning a binary code to the resulting vector or raster graphics data.

Display PostScript: The PostScript command set that renders images directly to the screen.

Display Type: Used for headlines and advertising copy, it is larger than 14 points.

Dithering: Simulating gray tones by altering the size, arrangement or shape of background dots.

Dot: The individual element of a halftone. Its size (density) can be related to the density of the original used to produce the halftone dot. The size of the dot is indicated by the percentage of the area it occupies from zero to one hundred percent. It may be several shapes including round, square or elliptical.

Dot Gain: An increase in the size of halftone dots that may occur as a result of errors or imperfections in any of the steps between screening an image and printing it onto paper. Common causes of mechanical dot gain are incorrect plate exposure, excessive tack or incorrect viscosity of printing ink, excessive ink film thickness, internal reflection of the ink, or too much pressure between the blanket roller and impression cylinder.

Dot Spread: In printing, a defect in which dots print larger than they should, causing darker tones or colors. (See Dot Gain)

Double Burn: The merging of two films into one using a contact screen camera. It is usually used to bring the black text into the black separation.

DPI: Dots Per Inch. A measurement of output device resolution and quality. Measures the number of dots a printer can print per inch both horizontally and vertically. A 600 dpi printer can print 360,000 (600 by 600) dots on one square inch of paper.

DSC: Document Structuring Convention. Also known as ADSC (Adobe Document Structuring Conventions) Postscript Format. Used as standards in the process of creating PostScript.

Dummy: A preliminary layout showing the position of illustrations and text as they are to appear in the final reproduction. A set of blank pages made up in advance to show the size, shape, color form and general style of a piece of printing. Also used to show imposition layout for stripping negatives.

Dynamic Range: A scanner's ability to capture an image's gradations from the lightest highlight to the darkest shadow.

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