Visibility aspects of VDUs in terms of contrast and luminance

Abstract

Abstract Abstract Characters on VDUs exhibit specific problems in terms of contrast and visibility evaluation. The photometric properties of CRT displays were analysed, resulting in the specification of local inner, local outer and mean character contrasts. On the basis of search experiments as well as of subjective appraisals it is shown that the inner detail contrast of characters is the determinant for the effect of contrast on visual performance and acceptance. The inner contrast also provides an adequate criterion to optimize the adjustment of contrast, including the effects of lighting in the room. In order to evaluate the visibility level of VDU characters an analytical model is presented based on the threshold numbers between critical character details. Recommendations are given for optimized adjustments of character contrast and background luminance.