Criteria for recommending lighting levels

Abstract

The effect of lighting on behaviour ranges from allowing simple detection of objects to creating moods and impressions. Lighting standards and recommendations for general applications should be based on the visibility (seeing) requirements where differences between individuals are minimal. Furthermore, lighting criteria or standards must evaluate the seeing process under stimulus conditions approximating those encountered in the real space. It is recommended that conspicuity, defined as: 'how well the detail stands out from the background', or ease of seeing be the metric for visibility. Subjective visual response criteria cannot be universally applied where significant differences in interpretations and evaluations between individuals and/or groups of individuals occur. Instead they should be treated as design options to be applied when they are important aspects of the intended function of the space. In discussing the above issues, the paper identifies the major categories of variables included in the perception of the visual environment and organises them logically with respect to their relationship in developing lighting criteria and standards. This analysis includes a breakdown of the visual processes into sensory and perceptual components. Key words: Conspicuity; contrast; illumination; lighting; lighting levels; suprathreshold visibility; vision.