Studies in Interior Lighting

The mechanism of interior lighting has been recently discussed in a Report of a Committee of the National Illumination Committee. The present paper records studies on three aspects of interior lighting: Adaptation, Revealing of Form and Texture, and Emphasis. It is proposed that effects of Adaptation should be taken into account in lighting calculations and values of Apparent Brightness used, for it is shown that figures of apparent brightness accord much better with experience than figures of absolute luminance, and explain anomalies which are found with absolute figures. A new method of calculation is outlined, whereby the effects of inter-reflection can be found very simply without complex theory and by means suitable for day-to-day work, so that the installation can be designed from a specification of apparent brightness distribution. The mechanism of the revealing of form and texture is discussed. Apparatus for the quantitative and systematic study of modelling and shadow are described; modelling indices and methods of portraying modelling capability of the lighting are proposed. Results in interiors of different types are given. Emphasis is a more subtle effect than modelling and does not lend itself so well to quantitative study; it is discussed qualitatively and more briefly. The techniques of experimental study of complete interiors are described and further general observations recorded. The effects of the factors discussed upon the lighting design for interiors are considered and possible techniques outlined. An appendix gives definitions of special terms used in the paper; a second appendix discusses techniques used, and a third describes the new method of calculation.