Abstract
A method is described for predicting the direct components of contrast rendition factor (CRF) and equivalent sphere illumination (ESI) prior to the installation of a lighting system. With the use of a card-programmable hand calculator the user of the computations is able to determine which luminaires are having the greatest effect, either positively or negatively, on CRF and ESI, and thus is able to try different locations and orientations. The theoretical considerations underlying CRF and ESI are reviewed and the equations necessary for calculating each quantity are presented. Four topics relating to CRF and ESI calculations are discussed; these are body shadow, intensity distribution curve interpolation, approximating equations for bidirectional luminance factors, and inverse square law approximations. The programmable hand calculator procedure is discussed and a sample design is given.
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