Light, photometry and illumination : a thoroughly rev. ed. of ''Electrical illuminating engineering'' (1912)
Barrows, William Edward, 1878-1960 · New York ; London : McGraw-Hill Book Co. · leaf 282
axisof this type of lighting equipment is shown in Fig. 158. Thispolar curve shows only the intensity of the light in differentdirections in a vertical plane and gives no clue as to the resultingillumination. The illumination due to one lamp placed 12 ft.above the reference plane is indicated by… … 654321012345678Feet from Midway between Sources. Fig. 160.—Illumination due to one and two 250-watt Tungsten lampsequipped with intensive, extensive and focusing types of reflectors. With a distance of 15 ft. between lamps, 12 ft. is the minimumheight of suspension which will secure approximately…
Light · Photometry · Electric lighting
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