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 perceived image quality judgments for CRT displays. The effects of five illumination conditions and two screen contrast polarities on image quality were assessed for seven CRT/anti-reflection filter configurations. Participants judged the image quality of the displays after reading text passages on the screen. Image quality judgments then were compared to ISO 9241-7 compliance classifications, as well as to two metrics inherent to the standard: screen image luminance ratio and specular reflection luminance ratio. The findings of this work (along with Kempic, Olacsi, and Beaton, 1998) contribute to a human factors justification of ISO 9241-7 and point up several shortcomings in this international standard. 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 understated in the ISO 9241-7 standard.