S Chiba¹, M Ohno¹, T Takai¹, M Suzuki¹, K Yanasima², A Kubo²
¹Tateyama Research Institute, Research Department, Chiba, Japan; ²National Rehabilitation Center for The Disabled, Department of Functional Training ‡V, Tokorozawa, Saitama, Japan
In order to develop signs with letters that are more easily recognizable to the visually impaired, the effect of the color difference between background and letters on sign visibility was analyzed, based on the characteristics of brightness and tint.
In this study, visibility was assessed in two ways: by determining how quickly letters on a test sign were visually recognized (shortest recognition time), and by determining how easily these letters were visually recognized (ease of visual recognition). Subjects consisted of 14 visually impaired patients and 16 volunteers with normal vision. Several signs were prepared, with varying brightness and tints of background and letter colors. The measure of the color difference was ΔE*; that is, the distance between two colors in the three-dimensional CIELAB color space.
As for the case of shortest recognition time, for the low-vision subjects, the greater the color difference between background and letter colors, the faster the visual recognition and the smaller the inter-subject variation; in other words, the closer the results were to those obtained in the healthy subjects. In the case of ease of visual recognition, for both visually impaired and healthy subjects, the greater the color difference, the easier the signs were to read.
There was a clear correlation between color difference and the two parameters; namely, the shortest visual recognition time and ease of visual recognition. Of the various constituent elements of color difference, a difference in brightness had the greatest impact on visual recognition.
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