A4.30.5 Finish and Contrast.
An eggshell finish (11 to 19 degree gloss on 60 degree glossimeter) is recommended. Research indicates that signs are more legible for persons with low vision when characters contrast with their background by at least 70 percent. Contrast in percent shall be determined by:
Contrast = [(B1 - B2)/B1] x 100
where B1 = light reflectance value (LRV) of the lighter area and B2 = light reflectance value (LRV) of the darker area.
Note that in any application both white and black are never absolute; thus, B1 never equals 100 and B2 is always greater than 0.
The greatest readability is usually achieved through the use of light-colored characters or symbols on a dark background.
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