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 194
two circles toward the center form a single scalemarked normal illumination angles which is used in problemsrequiring determination of the intensity of normal illuminationwhen the candle-power and angle are given, or when the intensityof illumination and height are given to read candle-power at… … Fig. 102.—Macbeths calculator. The two settings illustrated in Fig. 102 show the method ofobtaining the normal illumination intensity. In this case a16 candle-power lamp having a vertical downward candle-power of 7.2 is placed 5 ft. above the plane. The runner isplaced over 7.2 and zero on the…
Light · Photometry · Electric lighting
Internet Archive · Boston Public Library · Public Domain Mark 1.0. Free to use for anything.
