The Design of Numerals for Use in Counter-Type Instruments: A Review of the Literature
PURDUE UNIV LAFAYETTE IN
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The size of the critical detail in the numerals should be as large as is possible within the necessary practical limitations of overall numeral size. Within these limitations, the larger the numeral of any given type, the greater will be its visibility. The contrast between the numeral and its immediate background should be as great as it is possible to provide. The brightness contrast between the dial area and the surround should preferably yield a ratio of one. If this is not possible, a reduction of surround brightness below the level of the dial area reduces legibility only slightly. A situation which yields surround brightness greater than dial areas is to be strenuously avoided as this condition greatly reduces acuity. The brightness level of the numeral and its background should be as high as is possible in the situation obtaining. For greatest visibility, other factors held equal, numerals should be either black or white on opposite background. In order of decreasing visibility, in all cases inferior to black on white or white on black, are black on yellow, yellow-green, orange, green, red, blue-green, and blue.
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