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Guidelines for Electronic Preservation of Visual Materials

Appendix D: A Basic Digital Imaging Glossary

Pixel, Pel (abbreviation of Picture Element)

A dot that can vary in brightness and/or color.

Digitized Image
A two-dimensional array of pixels.

Color Image
A digitized image that can vary in brightness and color.

Grayscale Image
A digitized image which contains pixels which vary only in brightness in fine steps from black to white.

Binary Image
A digitized image which contains pixels which may only be fully black or white.

Spatial Resolution
The number of pixel spaces used in sampling a unit length of the image.

Tonal Resolution (or Pixel Depth)
The number of bits required to represent the number of distinguishable shades preserved in the image.

Table of Contents - Executive Summary - Introduction - Aspects of Collection Analysis - Guidelines - Scanning & Compression - Appendixes