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.

Target visibility under mesopic vision using a driving simulator

“…For this reason, we cannot assess differences in visibility beyond this 100% performance level, which indicate that constant VL values do not imply constant levels of suprathreshold visual performance. 39,40 Another visual performance model, the RVP model, is a broadly applicable model of visual performance that can be taken as a reasonable measure of foveal visibility for luminance in the mesopic and photopic ranges. 41 Different from the VL model, it provides a method for determining the speed and accuracy with which suprathreshold visual information can be processed.…”

Case studies of a camera-aided imaging method for evaluation of interior luminous environments

“…23,24 Rather, lighting levels for general applications should be based on the visibility (seeing) requirements, which deal with human vision and luminance-based light measurement. 23,25 The 10th edition Illuminating Engineering Society (IES) lighting handbook includes a new procedure for determining target illuminance and has introduced further categories with finer steps to allow adjustment of luminance requirement, considering factors such as minimum, average or maximum target values, uniformity targets, occupant age, and adjustment of photopic/mesopic adaptation. 26 The modern lighting profession is expected to transform from assessing light incident on planes to assessing light arriving on the eye.…”

“…23 Corresponding lighting criteria and evaluation methods, such as the camera-aided imaging method developed by this study, would evaluate the seeing process in the real space with design options to interpret the individual differences. 25 Conventional lighting measurements using metres are a point-by-point process which do not account for non-uniform electric lights and varying daylight in high resolution, and also do not provide information about the environment (e.g. size, shape, colour, contrast, shadow, etc.)…”

Luminance gradient for evaluating lighting

“…11 Corresponding lighting criteria must evaluate the seeing process in real space with design options to interpret the individual differences. 12 Therefore, such lighting criteria in the third stage need to be addressed based on luminance-based metrics. Luminance-based lighting evaluation has the potential to provide occupant satisfaction with the luminous environment and energy-saving improvements over traditional illuminance-based lighting design.…”