Data Compression - Technique of reducing the amount of storage required to hold a digital file to reduce the disk space the file requires and allow it to be processed or transmitted more quickly.

Deboss - To press an image into paper so it lies below the surface. Also called tool.

Deckle Edge - Edge of paper left ragged as it comes from the papermaking machine instead of being cleanly cut. Also called feather edge.

Densitometer - Instrument used to measure density. Reflection densitometers measure light reflected from paper and other surfaces; transmission densitometers measure light transmitted through film and other materials.

Density - (1) Regarding ink, the relative thickness of a layer of printed ink. (2) Regarding color, the relative ability of a color to absorb light reflected from it or block light passing through it. (3) Regarding paper, the relative tightness or looseness of fibers.

Density Range - Difference between the darkest and lightest areas of copy. Also called contrast ratio, copy range and tonal range.

Desktop Publishing - Technique of using a personal computer to design images and pages, and assemble type and graphics, then using a laser printer or imagesetter to output the assembled pages onto paper, film or printing plate. Abbreviated DTP.

Device Independent Colors - Hules identified by wavelength or by their place in systems such as developed by CIE. 'Device independent' means a color can be described and specified without regard to whether it is reproduced using ink, projected light, photographic chemistry or any other method.

Die - Device for cutting, scoring, stamping, embossing and debossing.

Die Cut - To cut irregular shapes in paper or paperboard using a die.

Digital Proofing - Page proofs produced through electronic memory transferred onto paper via laser or ink-jet.

Diffusion Transfer - Chemical process of reproducing line copy and making halftone positives ready for paste-up.

Digital Dot - Dot created by a computer and printed out by a laser printer or imagesetter. Digital dots are uniform in size, as compared to halftone dots that vary in size.

Direct Digital Color Proof - Color proof made by a laser, ink jet printer or other computer-controlled device without needing to make separation films first. Abbreviated DDCP.

Dog Ear - A letter fold at the side of one of the creases, an indentation occurs.

Dot Gain - Phenomenon of halftone dots printing larger on paper than they are on films or plates, reducing detail and lowering contrast. Also called dot growth, dot spread and press gain.

Dot Size - Relative size of halftone dots as compared to dots of the screen ruling being used. There is no unit of measurement to express dot size. Dots are too large, too small or correct only in comparison to what the viewer finds attractive.

Dots-per-inch - Measure of resolution of input devices such as scanners, display devices such as monitors, and output devices such as laser printers, imagesetters and monitors. Abbreviated DPI. Also called dot pitch.

Double Black Duotone - Duotone printed from two halftones, one shot for highlights and the other shot for midtones and shadows.

Double Bump - To print a single image twice so it has two layers of ink.

Double Burn - To expose film or a plate twice to different negatives and thus create a composite image.

Double Density - A method of recording electronically (disk, CD, floppy) using a modified frequency to allow more data storage.

Double Dot Halftone - Halftone double burned onto one plate from two halftones, one shot for shadows, the second shot for midtones and highlights.

Doubling - Printing defect appearing as blurring or shadowing of the image. Doubling may be caused by problems with paper, cylinder alignment, blanket pressures or dirty cylinders.

DPI - Considered as "dots per square inch," a measure of output resolution in relationship to printers, imagesetters and monitors.

Drawdown - Sample of inks specified for a job applied to the substrate specified for a job. Also called pulldown.

Drill - In the printing arena, to drill a whole in a printed matter.

Dropout - Halftone dots or fine lines eliminated from highlights by overexposure during camera work.

Dropout Halftone - Halftone in which contrast has been increased by eliminating dots from highlights.

Dry Back - Phenomenon of printed ink colors becoming less dense as the ink dries.

Dry Offset - Using metal plates in the printing process, which are etched to .15mm (.0006 in) creating a right reading plate, printed on the offset blanket transferring to paper without the use of water.

Dry Trap - To print over dry ink, as compared to wet trap.

Dual-purpose Bond Paper - Bond paper suitable for printing by either lithography (offset) or xerography (photocopy). Abbreviated DP bond paper.

Dull Finish - Flat (not glossy) finish on coated paper; slightly smoother than matte. Also called suede finish, velour finish and velvet finish.

Dummy - Simulation of the final product. Also called mockup.

Duotone - Black-and-white photograph reproduced using two halftone negatives, each shot to emphasize different tonal values in the original.

Duplex Paper - Thick paper made by pasting highlights together two thinner sheets, usually of different colors. Also called double-faced paper and two-tone paper.

Duplicator - Offset press made for quick printing.

Dylux - Brand name for photographic paper used to make blue line proofs. Often used as alternate term for blueline.