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Glossary of industry terms 2/3

Densitometer
A tool used to measure the amount of light that is reflected or transmitted by an object.
Diffusion dithering
A method of dithering that randomly distributes pixels instead of using a set pattern.

Digital
A system or device in which information is stored or manipulated by on/off impulses, so that each piece of information has an exact or repeatable value (code).

Digital camera
A device that captures an image on a CCD so it can be downloaded to and manipulated by a computer. It might also be called a filmless camera.
Digital Image
An image composed of pixels.
Dithering
A method for simulating many colours or shades of gray with only a few. A limited number of same-coloured pixels located close together is seen as a new colour.

DPI (Dots Per Inch)
The measurement of resolution of a printer or video monitor based on dot density. For example, most laser printers have a resolution of 300 dpi, most monitors 72 dpi, most PostScript image setters 1200 to 2450 dpi. The measurement can also relate to pixels in an input file, or line screen dots (halftone screen) in a prepress output film.
Driver
A software utility designed to tell a computer how to operate an external device. For instance, to operate a printer or a scanner, a computer will need a specific driver.

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EPS (Encapsulated PostScript)
A graphic file format developed by Aldus, Adobe, and Altsys to allow exchange of PostScript graphic files (image information) between application programs.

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Filters/Software
A program that accepts data as input, transforms it in some manner, and then outputs the transformed data. For example, a software program such as PhotoShop can take blurry pictures and filter them to produce a clearer picture.

Final Image Resolution
Generally speaking, the higher the resolution, the larger print you can make. Although print quality is affected by other factors as well, like exposure, colour quality, output quality, etc. It's not just how many pixels, but what you do with them!
Flat Bed Scanner
An optical scanner in which the original image remains stationary while the sensors (usually a CCD linear array) passes over or under it. The scanned material is held flat rather than being wrapped around a drum.

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GIF File Format
Stands for Graphic Interchange Format, a raster oriented graphic file format developed by CompuServe to allow exchange of image files across multiple platforms.

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Halftone Image
An image reproduced through a special screen made up of dots of various sizes to simulate shades of gray in a photograph. Typically used for newspaper or magazine reproduction of images.
Hue
A term used to describe the entire range of colours of the spectrum; hue is the component that determines just what colour you are using. In gradients, when you use a colour model in which hue is a component, you can create rainbow effects.

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ICC(International Colour Consortium)
Established in 1993 by eight industry vendors for the purpose of creating, promoting and encouraging the standardisation and evolution of an open, vendor-neutral, cross-platform colour management system architecture and components.

Image Processing
Capturing and manipulating images in order to enhance or extract information.

Image Resolution
The number of pixels per unit length of image. For example, pixels per inch, pixels per millimeter, or pixels wide.
Ink-Jet Printer
An ink-jet printer forms text and images out of dots created by jets of ink. Colour ink-jets support many different media sizes and output resolutions.

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JFIF(JPEG File Interchange Format
A minimal file format which enables JPEG bit streams to be exchanged between a wide variety of platforms and applications.
JPEG (Joint Photographic Experts Group)
A technique for compressing full-colour bit-mapped graphics JPEG Compression. A file compression standard established by the Joint Photographic Experts Group that uses a combination of DCT and Huffman encoding to compress images. JPEG is a "lossy" compression algorithm, meaning that it slightly degrades image quality.

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Mid Tones
The range of tones between the highlights and shadows of a photograph or halftone - between 30% and 75% value.
Moire
Undesirable screen patterns that occur when screened reproductions are made from halftone proofs.

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