Lighting and Color – Why Color Rendering Index is Important

Now that regular incandescent light bulbs are a thing of the past and LED’s and CFL’s are the new “go to” light bulbs, what can you expect your house to look like? The reason I am asking this question is because the colors in your home are going to appear differently than they do under good, old fashioned incandescent lighting. This is because of something know as CRI or Color Rendering Index, a scale of 0-100 where incandescent light bulbs are at the top of scale, 100.

Different light source have different CRI’s, all of which are compared to incandescent light bulbs, but non of which are equal to incandescent. Fluorescent and LED light sources vary in CRI between about 75 to about 85 with some LED’s approaching 90. Therefore things are going to look different depending on the CRI of you light bulb. Note the picture of the fruit and vegetables above. For most purposes, a CRI of 85 is considered good enough in residential applications.
This chart lists different light sources and their associated CRI values. At the bottom of the list is Low Pressure Sodium, a light source that was primarily used in highway lighting in the past. With this kind of lighting, a police officer could not tell the difference between blood and oil at an accident scene. CRI does make a difference!
New light bulb labeling laws are useful in selecting the correct light bulb with a satisfactory CRI. Please see this label and note that in addition to other important information the CRI value is shown as “Color Accuracy”.
Please be advised that higher CRI’s require a higher standard of manufacturing. In a fluorescent light bulb more expensive phosphors must be used and in LED’s higher quality computer chips must be used. Therefore you can expect to pay more for better quality light. There is no right or wrong, just be sure you understand the differences. 
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