What color is a blackbody?
- some pixel rgb values

Mitchell Charity <mcharity@lcs.mit.edu>
  > What color is a blackbody?
  >   > Different blackbody colors on the web
  >   > Blackbody colors - choosing parameters
  >   > Blackbody colors - intensity
  > What color are stars?

The idea: It would be nice to know what color a blackbody is at various temperatures.
Here is some help on converting blackbody temperature to color pixel rgb values.
 
 
 
 
 
   1000 K  #ff3800 
   1200 K  #ff5300 
   1400 K  #ff6500 
   1600 K  #ff7300 
   1800 K  #ff7e00 
   2000 K  #ff8912 
   2200 K  #ff932c 
   2400 K  #ff9d3f 
   2600 K  #ffa54f 
   2800 K  #ffad5e 
   3000 K  #ffb46b 
   3200 K  #ffbb78 
   3400 K  #ffc184 
   3600 K  #ffc78f 
   3800 K  #ffcc99 
   4000 K  #ffd1a3 
   4200 K  #ffd5ad 
   4400 K  #ffd9b6 
   4600 K  #ffddbe 
   4800 K  #ffe1c6 
   5000 K  #ffe4ce 
   5200 K  #ffe8d5 
   5400 K  #ffebdc 
   5600 K  #ffeee3 
   5800 K  #fff0e9 
   6000 K  #fff3ef 
   6200 K  #fff5f5 
   6400 K  #fff8fb 
   6600 K  #fef9ff 
   6800 K  #f9f6ff 
   7000 K  #f5f3ff 
   7200 K  #f0f1ff 
   7400 K  #edefff 
   7600 K  #e9edff 
   7800 K  #e6ebff 
   8000 K  #e3e9ff 
   8200 K  #e0e7ff 
   8400 K  #dde6ff 
   8600 K  #dae4ff 
   8800 K  #d8e3ff 
   9000 K  #d6e1ff 
   9200 K  #d3e0ff 
   9400 K  #d1dfff 
   9600 K  #cfddff 
   9800 K  #cedcff 
  10000 K  #ccdbff 
  10200 K  #cadaff 
  10400 K  #c9d9ff 
  10600 K  #c7d8ff 
  10800 K  #c6d8ff 
  11000 K  #c4d7ff 
  11200 K  #c3d6ff 
  11400 K  #c2d5ff 
  11600 K  #c1d4ff 
  11800 K  #c0d4ff 
  12000 K  #bfd3ff 
  12200 K  #bed2ff 
  12400 K  #bdd2ff 
  12600 K  #bcd1ff 
  12800 K  #bbd1ff 
  13000 K  #bad0ff 
  13200 K  #b9d0ff 
  13400 K  #b8cfff 
  13600 K  #b7cfff 
  13800 K  #b7ceff 
  14000 K  #b6ceff 
  14200 K  #b5cdff 
  14400 K  #b5cdff 
  14600 K  #b4ccff 
  14800 K  #b3ccff 
  15000 K  #b3ccff 
  15200 K  #b2cbff 
  15400 K  #b2cbff 
  15600 K  #b1caff 
  15800 K  #b1caff 
  16000 K  #b0caff 
  16200 K  #afc9ff 
  16400 K  #afc9ff 
  16600 K  #afc9ff 
  16800 K  #aec9ff 
  17000 K  #aec8ff 
  17200 K  #adc8ff 
  17400 K  #adc8ff 
  17600 K  #acc7ff 
  17800 K  #acc7ff 
  18000 K  #acc7ff 
  18200 K  #abc7ff 
  18400 K  #abc6ff 
  18600 K  #aac6ff 
  18800 K  #aac6ff 
  19000 K  #aac6ff 
  19200 K  #a9c6ff 
  19400 K  #a9c5ff 
  19600 K  #a9c5ff 
  19800 K  #a9c5ff 
  20000 K  #a8c5ff 
  20200 K  #a8c5ff 
  20400 K  #a8c4ff 
  20600 K  #a7c4ff 
  20800 K  #a7c4ff 
  21000 K  #a7c4ff 
  21200 K  #a7c4ff 
  21400 K  #a6c3ff 
  21600 K  #a6c3ff 
  21800 K  #a6c3ff 
  22000 K  #a6c3ff 
  22200 K  #a5c3ff 
  22400 K  #a5c3ff 
  22600 K  #a5c3ff 
  22800 K  #a5c2ff 
  23000 K  #a4c2ff 
  23200 K  #a4c2ff 
  23400 K  #a4c2ff 
  23600 K  #a4c2ff 
  23800 K  #a4c2ff 
  24000 K  #a3c2ff 
  24200 K  #a3c1ff 
  24400 K  #a3c1ff 
  24600 K  #a3c1ff 
  24800 K  #a3c1ff 
  25000 K  #a3c1ff 
  25200 K  #a2c1ff 
  25400 K  #a2c1ff 
  25600 K  #a2c1ff 
  25800 K  #a2c1ff 
  26000 K  #a2c0ff 
  26200 K  #a2c0ff 
  26400 K  #a1c0ff 
  26600 K  #a1c0ff 
  26800 K  #a1c0ff 
  27000 K  #a1c0ff 
  27200 K  #a1c0ff 
  27400 K  #a1c0ff 
  27600 K  #a1c0ff 
  27800 K  #a0c0ff 
  28000 K  #a0bfff 
  28200 K  #a0bfff 
  28400 K  #a0bfff 
  28600 K  #a0bfff 
  28800 K  #a0bfff 
  29000 K  #a0bfff 
  29200 K  #a0bfff 
  29400 K  #9fbfff 
  29600 K  #9fbfff 
  29800 K  #9fbfff 

Here is a more detailed table which includes chromaticity values and such.

If you can see this line, then its background isn't black, so the table above probably lacks color. Sorry. Perhaps you have an old browser?

Details

These values show color chromaticity (hue and saturation), but ignore brightness. Blackbody power output increases greatly with temperature, so also showing intensity is problematic. See Blackbody colors - intensity.

The black body spectrum was mapped to the CIE XYZ color space for integration using the CIE 1964 10-deg color matching functions. The XYZ to RGB conversion was done with sRGB's primaries and gamma correction, and a D65 whitepoint. A blackbody color tool hack was used to create a colorized datafile, and a plain text one.

Please let me know if 1976 u'v' chromaticity coordinates would be more useful than these 1931 x y ones.

Why did I hack out my own program when foo existed?
Mainly because different authorities were claiming different results, and there is nothing like rolling your own to make sure you understand what is going on. Feel free to email links to your favorite foo, and I'll add them below.

Links

What colour is the Sun? and Where's purple
BlackBody Physlet - interactive
Colour Rendering of Spectra (specrend) [uses an odd white-point for RGB values]
CIE 1931 X & Y Coordinates along the Black Body Curve [6500 K xy data was wrong in early March 2001]
Color Temperature and Sun Color at efg's Color Reference Library - a great collection of links and resources
(also includes Cromaticity Diagrams (and here) and a wavelength -> rgb approximation)
Color Science [uses an odd white-point (as of 2001-May-15)]
Converting Frequency to RGB
Blackbody Radiation - interactive
See Blackbody colors - choosing parameters for CMF links.
A blackbody applet under development

Notes

But why are mumble's colors different?
Old versions of BlackBody Physlet (such as Blackbody Radiation as of 2001-May-15) don't use D65.
Color Science's picture and programs (both FORTRAN and C) don't use D65 (as of 2001-May-15 - the white point is ignored).
Colour Rendering of Spectra's specrend doesn't use D65 (so the RGB values are odd).
Wolfram's interactive Blackbody Radiation uses some simplifying approximations.
Old cieppm's (netpbm version 9.9 and before) had a chromaticity diagram which didn't use D65.
ImagingScience's CIE'31 x & y's are CIE'31 without Judd and Vos corrections.

Thanks
My thanks to John Walker's Colour Rendering of Spectra (specrend) and Dan Bruton's Color Science, who's pages got me started. To the CVRL Color & Vision database. To Andrew Hamilton for What colour is the Sun?, which suggested I was not completely confused. And to efg for his Color Reference Library. Without them, this page would not have happened.

Other Links

Colour space conversion has a frequency -> RGB code.


Comments encouraged - Mitchell Charity <mcharity@lcs.mit.edu>

Notes:

Doables:
  Say Plank.  What else?
  Include u'v' 1976 chromaticity coordinates.
  Principled low bound.  Rod-ed graying out?  sRGB's 80 cd/m^2 monitor?
  Javascript K to color mapper.
  curves and code

History:
  2002-Nov-11  Fixed links broken by CVRL move.  Added a link.
  2001-Jun-22  Switched to sRGB from Rec.709
               (same primaries, similar matrix, different gamma correction).
  2001-Jun-04  on-line