Light, photometry and illumination : a thoroughly revedof ''Electrical illuminating engineering'' . he room type. In theformer installations six 40-watt tungsten lamps were usedgiving a total of 1914 lumens. There were six outlets distrib-uted over the ceiling and one lamp at each outlet. In the centerof room installation there were two outlets located near thecenters of two bays one of which was about two-thirds the sizeof the other. A 100-watt and a 150-watt tungsten were usedin these bays, respectively, and gave a total of 2075 the units except the indirect were mounted at a heig
Light, photometry and illumination : a thoroughly revedof ''Electrical illuminating engineering'' . he room type. In theformer installations six 40-watt tungsten lamps were usedgiving a total of 1914 lumens. There were six outlets distrib-uted over the ceiling and one lamp at each outlet. In the centerof room installation there were two outlets located near thecenters of two bays one of which was about two-thirds the sizeof the other. A 100-watt and a 150-watt tungsten were usedin these bays, respectively, and gave a total of 2075 the units except the indirect were mounted at a height of8 ft. 6 in. from the floor and the reference plane at which illu- Paper read before the Chicago Section of the Illuminating Engineering Society, Feb.,1912. 280 LIGHT, PHOTOMETRY AND ILLUMINATION mination measurements were made with a Sharp-Millar photom-eter was 30 in. from the floor. Obviously the indirect and semi-direct units were not suitablefor the distributed system, neither was the focusing type ofreflector suitable for the center outlet system. Hence thesecombinations were Coefficient of Reflection of WallsFig. 169.—Relative illuminating efficiencies for various types of reflectors,with medium colored (40 per cent, coefficient) ceiling. Small or mediumsized rooms with the distributed unit type of installation; Two interiors were used. For the light interior the ceilingand walls were covered with white mat cardboard such as isregularly used for the mat in picture-framing. It had a glaze-less surface slightly pebbly in character and had a reflectioncoefficient of For the dark ceiling and walls black cantonflannel cloth was used, having a coefficient of diffuse reflectionof PRINCIPLES OF INTERIOR ILLUMINATION 281 Tests were made with: (A) White ceiling and white walls. (B) Black ceiling and white walls. (C) White ceiling and black walls. (D) Black ceiling and black floor was of a light oak color. 65 50 4
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectlight, bookyear1912
