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 is also called as tool. 
 
Deckle Edge 
Edge of paper left ragged as it comes from the papermaking machine instead of being cleanly cut is also called as 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 image setter to output the assembled pages onto paper, film or printing plate. Abbreviated DTP. 
 
Device Independent Colors 
Hues 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 image setter. 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, image setters and monitors. Abbreviated DPI. 
 
Double Black Duotone 
Duotone printed from two halftones, one shot for highlights and the other shot for mid tones 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 mid tones 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, image setters and monitors. 
 
Drawdown 
Sample of inks specified for a job applied to the substrate specified for a job is also called pull down. 
 
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 is also called as suede finish, velour finish and velvet finish. 
 
Dummy 
Simulation of the final product is 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 colours is 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 blue line. 
 
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