Tip #521: What is Color Temperature?

… for Random Weirdness

Tip #521: What is Color Temperature?

From warm to cool, color temperature tells us where white light falls.

Image courtesy of Bhutajata - CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=44144928
Color temperature in degrees Kelvin from 1000° K to 12,000° K.

Topic $TipTopic

Color temperature is the measure of the perceived color of white light on a scale from warm (gold) to cool (bluish). These lighting facts might interest you, ’cause I found them interesting.

  • What we would consider “white” light is around 6500° K. (“K” stands for “Kelvin” which is a measure of absolute temperature indicating how much you would need to heat a “black body” to get it to glow at this color.)
  • The effective color temperature of the sun is about 5780° K .
  • The changing color of the sun over the course of the day is mainly a result of the scattering of sunlight and is not due to changes in the sun itself.
  • The Earth’s atmosphere scatters blue color frequencies more than warmer colors, which is why the sky is blue. (It’s called Rayleigh scattering, named after the 19th-century British physicist: Lord Rayleigh.)
  • Color temperature is meaningful only for light sources that generate light in a range going from red to orange to yellow to white to blueish white. It does not make sense to speak of the color temperature of a green or purple light.
  • Color temperatures over 5000 K are called “cool colors” (bluish), while lower color temperatures (2700–3000 K) are called “warm colors” (yellowish).
  • Bizarre fact: The temperature of a “warm” light is cooler than the temperature of a “cool” light.
  • Most natural warm-colored light sources emit significant infrared radiation.
  • A warmer (i.e., a lower color temperature) light is often used in public areas to promote relaxation, while a cooler (higher color temperature) light is used to enhance concentration, for example in schools and offices.
  • Most digital cameras today have an automatic white balance function that attempts to determine the color of the light and correct accordingly. While these settings were once unreliable, they are much improved in today’s digital cameras and produce an accurate white balance in a wide variety of lighting situations.

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2 replies
  1. Jim Turnbull
    Jim Turnbull says:

    Just six weeks ago I had an early cataract extraction from my right eye, with the implantation of a silicone IOL (Intra Ocular lens). As yet the left eye has no cataract. I was amazed to discover that if I close my left eye the white on this page is “whiter than white”, with a hint of a bluish tinge around 9,000ºK. Looking through my left eye alone – the human lens (aged 72y), the colours are much warmer, this white appearing around 6,000ºK. With both eyes open there is a pleasant compromise. It isn’t just paper that “yellows with age”!

    I wonder – should I be outsourcing my colour correction?

    Cataracts are an inevitability of the ageing process, dead lens cells that harden and obscure the light rays coming through the lens.

    • Larry Jordan
      Larry Jordan says:


      It depends upon the work you are doing.

      If you are making a living as a colorist, you need to make plans to sell your practice. If you are editing home movies, it doesn’t really matter. In between are a wealth of options, but getting a pair of younger, but qualified, eyes to check your work might be a good idea.



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