The Light Field in practice

Abstract

In the development of the lighting practice, progress has been made to eliminate bad lighting and to contribute to a visual comfortable scene. Metrics, and subsequent recommendations, have been established to provide uniform horizontal illuminance. In addition, performance-based metrics are developed. For example, various lighting levels for different tasks. However, the conventional metrics and current lighting standards fail to describe the spatial quality of light that provides a human observer with information about its surroundings contributing to one’s well-being. And so, increased emphasis is on three-dimensional light distribution in a space creating good lighting. Currently, renewed attention goes to the application of a theory to examine the visual appearance of light in a space: the light field. The light field can be subdivided in the light intensity, the light direction and diffuseness simultaneously. Hence, it is wondered to what extent the analysis of the light field is an effective alternative to predict visual comfort in a daylit office meeting space?

The research answers this main question in three parts, using literature review, in-field measurements and simulated data. The first part of the research concentrates on literature about the conventional visual comfort metrics (luminance Contrast Ratio and Daylight Glare Property), and the (mathematical) description of the light field. The second part of research deals solely with the light field. It examines how its properties can be measured and visualised, in researching the application of tool use. In part three knowledge about the conventional performance-based measuring techniques and the analysis of the properties of the light field (light intensity, light direction and diffuseness) are brought together and compared in a case study of a visual uncomfortable experienced office space.

Based upon the results obtained during the research, it is proven that the analysis of the light field is a promising candidate describing an uncomfortable setting in terms of light direction and diffuseness rather than luminance and illuminance. It is a view independent metric that can predict visual uncomfortable situations generated by a strong directional lighting combined with a low diffuseness, resulting in disturbing shades. Simultaneously, it is found that the current metrics for luminance Contrast Ratio and the simplified Daylight Glare probability, that try to predict the likelihood of visual comfort, lack a full description of the perceived level of visual comfort. Finally, the level of visual comfort for the human observer in the office space of the case study has been improved.

Keywords: daylight, light metrics, visual comfort, luminance contrast ratio, daylight glare probability, light field, light direction, light intensity, diffuseness, light field,