Exit sign recognition for color normal and color deficient observers

A stencil type exit sign has zero luminance contrast when the luminance of the background is equal to the luminance of the letters. In this case, color difference may be the only information available for the observer to recognize dhe sign. Another potential problem for the recognition of stencil type exit signs results from the increasing use of LEDs as a light source. Because they are a narrow band light source, care has to be exercised in the use of LEDs in exit signs, since some color deficient ("color blind") observers may not be able to readily perceive them. This paper presents data from eight color normal and eight color deficient observers who were asked to classify the orientation of an exit sign illuminated by LEDs in a two-alternative, forced choice procedure. The proportion correctly identified was measured over a range of luminance contrast, for four different LED target sources, and with a background of either broadband white, black, or the same LED source.