Abstract
It is usual in this country to publish details of an asymmetric light distribution in the form of an isocandle diagram with additional information regarding total light output or flux in the upper and lower hemispheres. Sometimes it is also necessary to give utilisation factor curves for street-lighting lanterns. It is convenient to have a method of obtaining the information for these curves by quick calculation from the isocandle diagrams.
The flux represented on the whole or part of an isocandle diagram may be calculated by reading the intensity at a number of points in a carefully chosen array and applying a simple formula. There is a number of different possible arrays and it is necessary to choose the one which is most suited to the particular calculation that has to be made. Two different types are described in this paper. One is suited to the calculation of the total light output of a lantern. The other is specially designed for the flux calculations involved in the production of utilisation factor curves.
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