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.

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.

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.

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.

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.

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.

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.

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

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.

Dummy
Simulation of the final product. Also called mockup.

Duplicator
Offset press made for quick printing.