What color is the Sun?
- chromaticity above the atmosphere

Mitchell Charity <[email protected]>
  > What color are the stars?
  >   > Star color - details
  >   > Star color - data comparison
  >   >   > Star color - data plots
  >   > Star color - blackbody approximation
  >   > What color is the Sun?

The Sun's chromaticity (seen from space, without atmospheric filtering) seems to be about
CIE x y: 0.326 0.338

 
So, a pixel color of      
  #fff3ea  
  		   
 

Here is a comparison with various whitepoints:
xy sRGB pixel color
Sun above atmosphere0.32590.3379#fff3ea
5770 K blackbody (a Sun approximation)0.32870.3397#fff1e6
Illuminant D65 (daylight, standard)0.31270.3290#ffffff
Illuminant D50 (bright incandescent light)0.34570.3585#ffebcd
Illuminant B ("direct sunlight")0.38400.3516#ffbfaa

These numbers were calculated using the 1985 Wehrli Standard Extraterrestrial Solar Irradiance Spectrum, the CIE 1931 2 degree Color Matching Functions as modified by Judd (1951) and Vos (1978) , and the sRGB color space primaries, gamma correction, and a D65 whitepoint. Using my blackbody color tool hack.

The choice of white point has a large effect...
0.3259 0.3379 #fff3ea - D65 whitepoint
0.3259 0.3379 #e0e8ff - D50 whitepoint

The choice of gamma correction has some small effect... (these are all D65)
#fff3ea - sRGB gamma correction
#fff2e8 - Rec.709 gamma correction

The choice of CMFs has some small effect... (these are all Rec.709 (D65))
0.3259 0.3379 #fff2e8 - CIE'31 2 degree CMFs with Judd Vos corrections
0.3239 0.3338 #fff1eb - CIE'64 10 degree CMFs
0.3231 0.3327 #fff1ed - CIE'31 2 degree original CMFs

What colour is the Sun? put a lot more effort into precision than I have done. Better underlying spectrum, better computation. Used CIE 1931 CMFs, and Rec.709.
0.3233 0.3326 #fff1ed - the site, CIE 1931 CMFs, and Rec.709.
0.3233 0.3326 #fff2ef - the same chromaticity, but converted to pixel color using sRGB instead.
0.3259 0.3379 #fff3ea - my numbers (for comparison)

Links

What colour is the Sun? and Where's purple
Solar Spectral Irradiance (Air Mass Zero) The 1985 Wehrli Standard Extraterrestrial Solar Irradiance Spectrum

Comments encouraged - Mitchell Charity <[email protected]> 

Notes:

Doables:
  Explain about whitepoints, D65, and resulting pink/bluishness.
  Ie, what does this page mean?

History:
  2002-Nov-11  Fixed links broken by CVRL move.
  2001-Jun-22  Changed to sRGB.
  2001-Jun-08  added D65/D50 contrast; push to ajsh's site.
  2001-Jun-05  added CMFs table
  2001-Jun-04  on-line