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Journal of the Optical Society of America A

Journal of the Optical Society of America A


  • Vol. 18, Iss. 2 — Feb. 1, 2001
  • pp: 412–420

Colorimetric and spectroradiometric characteristics of narrow-field-of-view clear skylight in Granada, Spain

Javier Hernández-Andrés, Javier Romero, and Raymond L. Lee, Jr.  »View Author Affiliations

JOSA A, Vol. 18, Issue 2, pp. 412-420 (2001)

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As part of our ongoing research into the clear daytime sky’s visible structure, we analyze over 1500 skylight spectra measured during a seven-month period in Granada, Spain. We use spectral radiances measured within 3° fields of view (FOV’s) to define colorimetric characteristics along four sky meridians: the solar meridian and three meridians at azimuths of 45°, 90°, and 315° relative to it. The resulting clear-sky chromaticities in 44 different view directions (1) are close to but do not coincide with the CIE daylight locus, (2) form V-shaped meridional chromaticity curves along it (as expected from theory), and (3) have correlated color temperatures (CCT’s) ranging from 3800 K to ∞ K. We also routinely observe that sky color and luminance are asymmetric about the solar meridian, usually perceptibly so. A principal-components analysis shows that three vectors are required for accurate clear-sky colorimetry, whereas six are needed for spectral analyses.

© 2001 Optical Society of America

OCIS Codes
(010.1290) Atmospheric and oceanic optics : Atmospheric optics
(330.1710) Vision, color, and visual optics : Color, measurement
(330.1730) Vision, color, and visual optics : Colorimetry

Original Manuscript: May 22, 2000
Revised Manuscript: August 25, 2000
Manuscript Accepted: August 25, 2000
Published: February 1, 2001

Javier Hernández-Andrés, Javier Romero, and Raymond L. Lee, "Colorimetric and spectroradiometric characteristics of narrow-field-of-view clear skylight in Granada, Spain," J. Opt. Soc. Am. A 18, 412-420 (2001)

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