Color Temperature

Color Temperature

What is “Color Temperature“, and how does it relate to CRI, or the Color Rendering Index?

We know CRI to be an international measurement scale or rating of how accurately an artificial  light source renders, or shows the color of an object (often called its “color appearance” ) as compared to daylight, which is capable of depicting, rendering or showing the widest range of colors. Thus, CRI rates, describes or measures how the  colors of objects  appear (compared to daylight) under a specific light source…IE, in a given light.

Color temperature however refers to the actual color and type of  light emitted by a particular light source.  High color temperatures, those over 5,000K (K = Kelvin) are termed cool colors  and are bluish white, while lower color temperatures (2,700–3,000 K) are called warm colors  and are yellowish white through red.

Yes, counter-intuitively, the higher color temperature describes a cooler color, while a lower color temperature describes a warmer hue. When considering interior lighting,  color temperature can play a significant role in how we feel and function in a space.  A warmer light, which has a  lower color temperature, can  promote our relaxation, while a cooler  light with a higher color temperature may enhance or help to increase our concentration.

Thus, color temperature refers to the color of light, and CRI refers to the ability of a light source to render the color of objects in a manner comparable to the way daylight does/would.

Whew…what a mouthful!

The rub?  The color rendering index can be used as a basis of comparison between light sources only if they have the same color temperature. To compare light sources, or to compare an artificial light source to daylight, said artificial light source must have the same color temperature as the daylight to which it is being compared.  Remember, daylight renders, or makes visible, the widest range of colors…and there are yet many more colors in the light spectrum that we cannot see with our naked eyes.  We are not able to see the entire light (thus color) spectrum. Light values beneath the visible part of the spectrum are referred to as infrared, and above the spectrum as ultraviolet.

CCT, or Correlated Color Temperature  is expressed in Kelvin, and describes whether a white light source appears more yellow/gold, or more blue.  Thus, it  is  a numerical description of a  light’s color appearance.  It can be used as a means of correlating the color of an artificial light source with the color of daylight. “The correlated color temperature (CCT) is a specification of the color appearance of the light emitted by a lamp, relating its color to the color of light from a reference source when heated to a particular temperature, measured in degrees Kelvin (K).

Here, we bring our discussion of Color Temperature, and its relationship to CRI to a close, at least for the moment.  It is a complex subject, but one that can come into play when dealing with any matters of color and light in the realms of photography, film, video, interior design, theater, the visual arts, and many other areas.  Good for us to have some idea of what the terms mean!


I hope that this series of posts on the relationship between Color and Light has helped to demystify it for you…at least to some extent. As much as we can learn, observe and discover, we will never know it all…and maybe that is as it should be.  Some things, such as the majesty and magnificence of the natural world should retain some mystery…no matter how much physics we attempt to wrap our minds around.




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3 CommentsLeave a comment

  1. Very well written and very concise. Color temperature and light are certainly subjects that are complex and a bit mystifying. Even well trained colorists have a difficult time understanding them. Well done, this is great information for all!

    • Thank you Teresa!
      I love the rigor of delving into these aspects of color, and working towards their “demystification”.
      Thank you for reading and commenting.

  2. […] Color Temperature ( […]

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