Light, photometry and illumination : a thoroughly revedof ''Electrical illuminating engineering'' . ightness flicker, and in fact the flicker photometer is theonly form in which simultaneous contrast is fully eliminated,which is another good reason for employing it inheterochromaticcomparisons. A series of researches by Dr. Ives^ are of great value in solving Trans. Ilium. Eng. Soc, Vol. 5, p. 711, 1910. 100 LIGHT, PHOTOMETRY AND ILLUMINATION the problems in heterochromatic photometry. In these inves-tigations Dr. Ives used the flicker and equality of brightnessarrangements for obtaining the l
Light, photometry and illumination : a thoroughly revedof ''Electrical illuminating engineering'' . ightness flicker, and in fact the flicker photometer is theonly form in which simultaneous contrast is fully eliminated,which is another good reason for employing it inheterochromaticcomparisons. A series of researches by Dr. Ives^ are of great value in solving Trans. Ilium. Eng. Soc, Vol. 5, p. 711, 1910. 100 LIGHT, PHOTOMETRY AND ILLUMINATION the problems in heterochromatic photometry. In these inves-tigations Dr. Ives used the flicker and equality of brightnessarrangements for obtaining the luminosity curves showing thecomparison of the spectral colors with w^hite light. The appar-atus was so designed that it could be used for both the equalityof brightness and the flicker methods without disturbing any ofthe critical conditions. The tw^o illuminations used were 10 and 250 units, where a unitis the illumination of 1 meter-candle on a surface of magnesiumoxide as viewed through an artificial pupil of 1 square millimeterarea. Because of the small area of this pupil opening the effec-. t -•« / \ .^f-. -^?^^ / \ \ P\ \\ // IJ V \ \\ \ V- \ ?7// \ ; \ \ \/ ,.. r ;\A v 1 . * » « H *? X < Mean Etiualitv of Brightness Method [UimunationioU Lmis \S\\ \\ i \ ? \ f^ fJ. Xellow Orange Ked Green Yellow Orange Ued Fig. 44.—Relative luminosity of Fig. 45.—Relative luminosity of monochromatic light. (flicker monochromatic light (equality of method). brightness method) tive illumination was probably about these values. A cir-cular photometrical field of 16 mm. in diameter at 24 cm. fromthe eye was chosen. This field subtended an angle of degrees,approximately the size of the yellow spot of the retina. Readings were taken with each type of photometer for twelvepoints in the spectrum alternating on the red and green average readin
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectlight, bookyear1912
