Abstract
The level of brightness contrast required for letter recognition in daytime lighting conditions is a function of letter size, colour contrast and the observer's age. The average contrast required by older subjectswas found to be 2, 13 times the contrast required by younger subjects, older individuals could not discriminate colour differences as well as younger subjects. Older subjects were asked to rate a small set of CRT colours in terms of how desirable they would be for night time instrument panel lettering, green and blue- green were the most preferred colours while red and blue were the least.