The luminous flux field as a basic concept for interior lighting design

Abstract

It is proposed that the process of interior lighting design be defined as creating a three-dimensional luminous flux field within the volume of an enclosed indoor space. This luminous flux field can be divided into two components, an indirect flux field and a direct flux field, and making this separation presents a remarkable insight into the lighting design process. The space, its contents and its occupants are revealed by the indirect flux field; the indirect flux field is generated by the direct flux field; and the direct flux field, which may be derived from the indirect flux field by calculation, specifies the performance of the lighting installation. This enables a practitioner to describe lighting design objectives in terms of peoples’ subjective responses to their lit appearance, and, where these objectives can be specified in quantitative terms, to define aspects of the indirect flux field that would achieve them. The direct flux field that would optimally generate this indirect flux field is determined by a calculation procedure, and this provides a photometric performance specification for the lighting installation. For the sake of simplicity, this paper considers only electric lighting, but opportunities for extending the procedure to include daylight and other lighting design objectives are discussed.