About LED Lighting, Ask a LED Tech Articles, CRI color rendering index

Ask a LED Tech Articles - What is CRI? One of the questions we are frequently asked about LED lighting pertains to the color rendering index.

March 25, 2015

Color Rendering Index or CRI is one of those terms you might see when looking at the specifications of LED lighting fixtures or LED light bulbs. It isn't a term most consumers were aware of until recently, as LEDs have not been a mainstream lighting source until the last 5-10 years. Before that there wasn't a strong need to be concerned with CRI in most household lighting applications.

The Color Rendering Index is very simple. It is a numerical scale from 0-100. It is an indicator of how well the light source will show the true or natural color of an object. If the source of the light were the sun, the the index would read as 100 since objects viewed in direct sunlight appear in their absolute true color. With most incandescent lights that was also true so there was very little use for the CRI for the consumer until the emergence of alternative sources, such as the LED. However, as with fluorescent light sources, in the beginning, light produced by LEDs did not show the true color of objects. People would describe the light as 'too blue'. Over time as LEDs gained popularity and recognition, that has changed drastically. The CRI is now helpful to guide consumers as well as manufacturers.

When you purchase an LED fixture or bulb you should look for this specification. Until very recently a CRI of 75 or 80 was considered to be good. Now, it is becoming very common to see the CRI at 85 or higher. The closer to 100 the CRI is, the better the colors will appear. Higher CRI LED light bulbs and fixtures typically cost more. Those higher CRI LED light sources are more critical in commercial applications such as retailers where clothing is displayed or food presented. A higher CRI LED bulb is better in bathrooms or dressing rooms where makeup is being applied and accessories such as neckties are being selected. In the workplace, higher CRI LED light sources produce an environment which makes people feel more energetic and productive. Conversely, if you are looking for a LED light bulb to replace the incandescent bulb on your back porch fixture, you can often do with a more economical, lower CRI light bulb.

Interestingly enough, the CRI is independent of the Color Temperature. For example, an LED bulb with a color temperature of 5000K cool white does not mean automatically that the CRI will be higher than a 2700-3000K warm white LED bulb. See our recent blog on Kelvin temperatures for more information on that topic.

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By: John Cody

Tags: About LED Lighting, Ask a LED Tech Articles, CRI color rendering index

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