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Journal of the Optical Society of America

Journal of the Optical Society of America

  • Vol. 29, Iss. 1 — Jan. 1, 1939
  • pp: 1–9

Artifial Daylighting for Color Grading of Agricultural Products

DOROTHY NICKERSON  »View Author Affiliations

JOSA, Vol. 29, Issue 1, pp. 1-9 (1939)

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DOROTHY NICKERSON, "Artifial Daylighting for Color Grading of Agricultural Products," J. Opt. Soc. Am. 29, 1-9 (1939)

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  1. Light from a clear blue sky is very generally called "glaring," yet, as can be seen from Tables I and II, the illumination intensity for such days is well below that of slightly cloudy, or even of overcast days. It has seemed obvious that high color temperature should be avoided.
  2. Anyone having use for detailed data for horizontal and 45° positions can obtain photostatic copies of summary tables by writing to the Bureau of Agricultural Economics, United States Department of Agriculture, Washington, D. C.
  3. Dr. A. H. Pfund suggested zinc oxide for this purpose, mixed with cold water or as little binder as possible, Dr. G. F. A. Stutz, contributed the material, and Mr. E. F. Hickson, National Bureau of Standards, mixed it in one his mills.
  4. I. G. Priest, "Report of the Work of the Colorimetry Committee of the International Commission on Illumination and the Actions Taken at the Meeting in Cambridge, England, September 1931," J. Opt. Soc. Am. 22, 431 (1932). Deane B. Judd, "The I.C.I. Standard Observer and Coordinate System for Colorimetry," J. Opt. Soc. Am. 23, 365 (1933). In connection with the adoption of 6500°K as representative of average daylight, reference should be made to the discussion of "White Light" prepared and circulated by Priest within this country in July 1931 as a part of the preparation for action on that subject by the I.C.I. Colorimetry Committee which met and adopted standards the following September. I.C.I. File Reference Document "15 U.S. 6" (National Bureau of Standards file).
  5. Perhaps this may only indicate that there is more difference in color temperature than has been supposed between overcast sky from the south (found by Gibson to be closely 6500°K) and overcast sky from the north. It seemed to the writer, in suggesting I.C.I. "C" Illuminant for a first trial—it having been adopted as a standard for average daylight—that it would probably be close to the color of an overcast sky.
  6. Dr. W. E. Forsythe supplied figures for color temperature of 500-, 750- and 1000-watt lamps of type PS52 used. (Letters of December 20, 1937 and March 31, 1938.) These lamps are rated at 1000-hour life. Regarding color temperature change in tungsten lamps see: Deane B. Judd, "Changes in Color Temperature of Tungsten Filament Lamps at Constant Voltage," J. Opt. Soc. Am. 26, 409 (1936).
  7. Deane B. Judd, "Estimation of Chromaticity Differences and Nearest Color Temperature on the Standard 1931 I.C.I. Colorimetric Coordinate System," J. Opt. Soc.Am. 26, 421 (1936). H. P. Gage and Norman Macbeth, "Filters for Artificial Daylighting, Their Grading and Use," Trans. I.E.S. 31, 995 (1936).
  8. See also, Irwin G. Priest, "Proposed Scale for Use in Specifying the Chromaticity of Incandescent Illuminants and Various Phases of Daylight," J. Opt. Soc. Am. 23, 41 (1933). The proposal made in this paper should receive serious consideration. It would be much easier to work in Priest units of microreciprocal degrees of color temperature than in color temperature itself. For reference these units are indicated in Fig. 5 as "mireds."
  9. A. C. Hardy, Handbook of Colorimetry, 1936. The Abbot data in this book (Tables VI and VII) were prepared by Dr. K. S. Gibson and supersede previously published data.
  10. The most recent paper by Luckiesh, Taylor and Kerr which gives these energy curves, gives curves also for Mercury and tungsten lamp combinations, and for Ivanhoe Trutint noon sunlight and north sky light: "Artificial White Light," General Electric Review, February 1938. See also A. H. Taylor, "The Color of Daylight," Trans.I. E. S. 25, 154 (1930), and "Spectral Distribution of Energy in Common Illuminants," General Electric Review, Sept. 1934.
  11. Davis-Gibson, "Filters for the Reproduction of Sunlight and Daylight and the Determination of Color Temperature," Misc. Publication, National Bureau of Standards, No. 114, 1931.
  12. Unless otherwise noted, transmission curves for filters given in this paper were measured on a General Electric Recording Spectrophotometer, some in the laboratories of the Interchemical Corporation, some at the National Bureau of Standards.
  13. Similar to curves shown in bulletins describing Sunshine Carbon. See also a recent paper by Bowditch and Downes, "Spectral Distributions and Color-Temperatures of the Radiant Energy from Carbon Arcs Used in the Motion Picture Industry," J. Soc. Mot. Pic. Eng. 30, No. 4 (1938).
  14. G. E. Inman, "Characteristics of Fluorescent Lamps," Trans. I. E. S. paper presented before the thirty-second annual convention of the Illuminating Engineering Society, August 29–31, 1938.

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