Lighting Research & Technology

Practical design calculations must be simple and high accuracy is rarely required. The widely used lumen-method is becoming increasingly dependable; local lighting methods are nevertheless indispensable. The applicability of the point source concept is discussed, and the principles of line source calculations using the sector flux concept are briefly given. An example shows the combined use of point and line source methods. Flux relations are summarized.

A formulation for the practical pre-determination of direct discomfort glare is proposed on the Harrison-Meaker pattern, but based on later laboratory research. A summation theorem is postulated, which states that a glare rating must be proportional to source area if simple additivity is desired. A location coefficient chart has been derived from Luckiesh-Guth's position indices, and αΛ-charts are given which allow for orientation as well as position of glare sources. An analytical expression for the location coefficient dispenses entirely with charts.