Abstract
The inter-reflection method of lighting design has been available since 1946, but its value has been reduced, due to the difficulty in separating the total flux from the luminaires into wall, ceiling and floor components. Methods so far suggested involve either the use of non-standard photometric data or the approximation of the intensity distribution to one of the few distributions for which tables have been subsequently calculated. The paper develops a method based on a simple analysis of the polar diagram.
The distribution of flux over the room surfaces is related to “surface distribution factors,” which are calculated and given in graphical form for an extended range of standard distributions similar to those used by Harrison and Anderson in the calculation of coefficients of utilisation. The factors are related to the positions of the luminaires with respect to the surface to which they refer and this relationship is summed up in the form of a “surface coefficient.”
Various methods of calculating distribution factors are mentioned, and an example of lighting design using the factors is given and discussed.
The advantages of the inter-reflection method and the degree of accuracy to be expected are also discussed.
Appendices, aimed at increasing the usefulness of the paper, are given, including definitions of new terms and an analysis of published performance data for a wide variety of luminaires (lighting fittings). These analysed data are given in a form suitable for use in the method described in this paper
Get full access to this article
View all access options for this article.