A Versatile Method of Calculating Illumination and Brightness
Our system of computing interior illumination is based on three fundamental concepts, the maintenance factor, the room index (or room ratio), and the coefficient of utilization. If the correct value for each of these three variables is used in the calculations, the predicted illumination will match the measured quantity. Probably the largest errors in the predicted illumination are caused by misjudging the maintenance factor. Adequate information is not available for use in evaluating the quantity and a comprehensive study coupled with extensive experimental work is needed. While experimental checks are necessary in studying the other two concepts, the basic work is of a mathematical nature. These two subjects will be discussed in detail.