Calculating Correlated Color Temperatures Across the Entire Gamut of Daylight and Skylight Chromaticities

Abstract

Natural outdoor illumination daily undergoes large changes in its correlated color temperature (CCT), yet existing equations for calculating CCT from chromaticity coordinates span only part of this range. To improve both the gamut and accuracy of these CCT calculations, we use chromaticities calculated from our measurements of nearly 7000 daylight and skylight spectra to test an equation that accurately maps CIE 1931 chromaticities x and y into CCT. We extend the work of McCamy [Color Res. Appl. 12, 285-287 (1992)] by using a chromaticity epicenter for CCT and the inverse slope of the line that connects it to x and y. With two epicenters for different CCT ranges, our simple equation is accurate across wide chromaticity and CCT ranges (3000-10(6) K) spanned by daylight and skylight.

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Document Details

Document Type
Technical Report
Publication Date
Sep 20, 1999
Accession Number
ADA529863

Entities

People

  • Javier Hernandez-andres
  • Javier Romero
  • Raymond L. Lee Jr.

Organizations

  • United States Naval Academy

Tags

Communities of Interest

  • Energy and Power Technologies

DTIC Thesaurus Topics

  • Accuracy
  • Algorithms
  • Altitude
  • Chromaticity
  • Color Temperature
  • Daylight
  • Equations
  • Errors
  • High Temperature
  • Light Sources
  • Measurement
  • Optical Phenomena
  • Optical Properties
  • Optics
  • Scattering
  • United States
  • United States Naval Academy

Fields of Study

  • Physics

Readers

  • Calculus or Mathematical Analysis
  • Vision Science/Vision Psychology/Cognitive Neuroscience.