Thomy Nilsson

Harnessing Color for Effective Presentation of Images and Text (2009)

Color combined with graphics enables presenting enormous amounts of information in a manner that can readily be understood.  Yet until recently it was generally believed that color had no effect on the legibility of visual graphics.  Because legibility had been defined in terms of processing speed, previous measurements of color legibility had been confounded by the fact that color information was transmitted by slower neural pathways than those for brightness.  Therefore these experiments found that only differences in brightness mattered.  To avoid this problem, I defined legibility in terms of the number of visual pathways needed to convey information.  Visual presentations that required fewer pathways to be seen clearly were defined as being more effective than presentations that required more pathways.  (This is simply a reversal of how visual acuity is defined in the 20/20 system.)  At the UPEI-Health Canada Legibility Testing Facility, we use distance thresholds to indirectly measure the required number of visual pathways.  Early data on legibility of colored graphic symbols on colored backgrounds found color combinations that were significantly more effective than black/white.  This proved that color does affect legibility.  The results of a three-year project involving 48,000 measurements by 12 persons with normal color vision are presented.  Examples of the effectiveness of various color combinations will be demonstrated.  Discussion includes effects of certain graphical characteristics and implications for standardizing color legibility.

Thomy Nilsson, Ph.D., is an emeritus professor of Psychology at the University of Prince Edward Island.