Color Rendering Index

a guest post by Lisa J. Reed, Lighting Designer

Color is much more complex than it first appears. Here's a quick science lesson for you: different colors are actually just different wavelengths within the visible light spectrum. To see a particular color, you actually need three things:

  1. An object that will reflect a particular wavelength
  2. A light source that contains the wavelength
  3. A receptor (your eye) that can perceive that wavelength
If the light source doesn't deliver a particular color or if the object doesn't reflect that color OR if the receptor can’t perceive the color (as in infrared or ultraviolet) you don’t see the color.

If the light source doesn't deliver a particular color or if the object doesn't reflect that color OR if the receptor can’t perceive the color (as in infrared or ultraviolet) you don’t see the color.

In the previous post we looked at the color temperature, or color of the light. That actually has very little to do with color rendering, which is the color of the objects under the light. Understand the difference? Either a warm source like incandescent or a cool source like daylight can render the color of objects nearly perfectly. But not all white light is created equal. Some light sources don’t contain a full and complete spectrum of colors. So if an object is viewed under a light source that doesn't include all of that object’s colors, its color won't be 100% accurate when viewed under that light source.

The photos below show differences in color rendering. The bunting is the same, but the colors appear more muted under certain sources and more vibrant under others. It is important to know not only whether a source is warm or cool (color temperature) but also how it renders the objects under its light (color rendering.)

Color is much more complex than it first appears. Here’s a quick science lesson for you: different colors are actually just different wavelengths within the visible light spectrum. To see a particular color, you actually need three things. Color is much more complex than it first appears. Here’s a quick science lesson for you: different colors are actually just different wavelengths within the visible light spectrum. To see a particular color, you actually need three things.
 

Now let's revisit the lighting facts labels.

In this label, the color of the lamp is listed, but not its color accuracy.
Color temperature is a term that is commonly referenced by photographers and lighting professionals, but it is all Greek to the general public. As consumers move away from incandescent lamps, they need to have at least a basic understanding of the Color T
In this label, both are listed.
Have you seen the new lighting facts labels?

As a consumer of today's complex lighting sources, you need to know both. The current CRI (color accuracy) scale goes to 100. In most cases, choose the highest number you can afford. The industry is currently working to create an improved measurement for color accuracy, so if you have the opportunity to try out multiple sources to see how they look in your final application, that is even better. Check color accuracy to avoid disappointment!

Do you have a story about color accuracy disappointment? How about a time when you couldn't find your car in a parking lot because the lights made it difficult to see the color of the cars?

 

Lisa J Reed photo - Lighting Blog

Lisa J. Reed has been attracted to lighting (like a moth to a flame) for 20+ years. She is the Founding Principal at Envision Lighting Design, LLC in St. Louis, where she designs, teaches, and writes about architectural lighting.

 

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