In microform records, the relationship between the size of a document and the size of a microimage. Usually expressed as 16x, 24x, etc. or as 16:1, 24:1, etc. Varies from low (below 15x), medium (15x through 30x), high (above 30x through 60x), very high (above 60x through 90x), and ultra high (above 90x). See also MAGNIFICATION RATIO.