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Cashen Diverse Solutions - Glossary [R]

Raster File

See "bitmap"


The technique of tracing over a raster scan image with a vector CAD compatible layer.


Redundant Array of Inexpensive Disks
There are several implimentations all designed in varying degrees of sophistication to allow continous real time access to stored data with full data integity even if there is a hardware failure in the disk subsystem. Such a failure can be corrected by replacing the damaged disk (the system is still live and data being accessed) and allowing the system to rebuild the data that was stored on the original faulty disk.


Offset lithograph, inkjet and laser printers and computer screens all compose their images of dots. Resolution is the number of dots or pixels per unit length. Dots per inch (DPI) for printing or pixels per inch (PPI) for scanning.

Roll Film

An original is first photographed onto a roll of film in negative format. The film may be either 35mm or 16mm wide. Larger format drawings and documents (normally anything bigger than A3) are usually filmed on 35mm with up to 500 images per roll. 16mm film is generally used for smaller originals with 2500 plus images per roll. Roll films are sometimes duplicated onto thinner base material and these may hold even more images. Occasionally a positive film is produced from the original. Some microfilm viewing devices use 16mm stock held inside a cassette.


A type of 16mm camera where the document is fed through rollers in a camera body and the film rolls in synchronisation with it to create a microfilm image. Suitable for A4 sheets and cheques etc at high speed, but quality not as reliable as planetary process.
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