Human Factors Assessment of ISO 9241-7, “Requirements for Displays with Reflections.”

This work evaluated the recently-published ISO 9241-7 “Ergonomic requirements for office work with visual display terminals (VDTs) - Part 7: Requirements for display with reflections” technical standard in terms of the readability of text passages presented on CRT displays. The effects of five illumination conditions and two screen contrast polarities on Tinker Reading Test scores (i.e., reading times and errors) were assessed for seven CRT/anti-reflection filter configurations. The readability scores were compared to ISO 9241-7 compliance classifications obtained for the seven CRT displays, as well as to two contrast metrics underlying the ISO 9241-7 compliance classifications: screen image luminance ratio and specular reflection luminance ratio. The findings show that only the specular reflection luminance ratio for large-area, negative polarity correlated with reading times. The present findings, along with those in a companion work (Olacsi, Kempic, and Beaton, 1998), contribute to the understanding of CRT viewability in glare environments and point out some shortcomings of ISO 9241-7. In particular, the findings indicate that specular reflections from CRTs degrade image quality more than do diffuse reflections, and, therefore, the importance of specular reflections is underemphasized in the ISO 9241-7 standard.