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Ask a LED Tech Articles – What is CRI?

One of the questions we are frequently asked about LED lighting pertains to the colour rendering index.

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 colour of an object. If the source of the light were the sun, the index would read as 100 since objects viewed in direct sunlight appear in their absolute true colour. With most incandescent lights that were 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, the light produced by LEDs did not show the true colour 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 a 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 colours will appear. Higher CRI LED light bulbs and fixtures typically cost more. That 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 to 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 Colour Temperature. For example, a LED bulb with a colour 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. Do you have a question about LED lighting we can answer for you here? Please email us.

By: John Cody