PHOTOMETRIC LABORATORY (Feb, 1947)
A reflector on an electric lamp controls light in much the same way that the nozzle on your garden hose controls water. One type scatters light like a fine spray; another throws a high-intensity beam like a stream of water.
To help illuminating engineers find out exactly how any reflector performs, the Benjamin Electric Manufacturing Company built this scientific darkroom in Des Plaines, Ill. A movable photometer stand on a track carries light-sensitive cells, which can measure the illumination from a reflector placed in any part of the room or suspended from the ceiling. The floor is marked off in squares for accurate measurement of distance. Ceiling lights are turned off when a test is being made. If a powerful lamp is being tried, the slotted sector disk is rotated to kill a known percentage of light and protect the cells from being “overwhelmed.”