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Color Rendering Index Representation

Shedding a Little Light on CRI

If you’ve been shopping for LEDs, or any type of lighting recently, you may have come across the term “Color Rendering Index” or “CRI.” Knowing a lights CRI can help you make a better, informed purchase. But, this isn’t a household term, and most people don’t know what it means. Here, we’ll go over everything about CRI so that the next time you come across this term, you know exactly what it means. 

What is Color Rendering?

Before we can get into what the CRI is, we first need to discuss color rendering. Color rendering is the process by which your eyes define color. This action is severely influenced by the light source and light quality.  It further defines how well subtle variations in color shades are presented by the light source. 

When people talk about an object’s color, they are usually referring to the appearance of the object (red, pink, purple, brown, white) or a light source (warm-white, cool-white). Although color appearance seems to come from the physical characteristics of an object, in reality, it’s just the way a certain signal is interpreted by the visual system. More specifically, color appearance is the result of calculations performed by three separate “color channels” in the visual system. Each channel takes the same radiant power falling on the retina and processes it slightly differently, resulting in the appearance of different colors.

What Is The Color Rendering Index (CRI)?

Cri

CRI,  or color rendering index, was established many, many years ago by the International Commission on Illumination. It provides a way to evaluate how effectively light sources display the true color of an object. It is also a measure of how well you’ll be able to see a color beneath a certain light source, in comparison to how well you would be able to see the same thing under the ideal light source, sunlight. 

Measured on a scale of 1 to 100, CRI is the only universally recognized color rendering metric. However, it’s absolutely essential to differentiate CRI from color temperature, which refers to how warm or cold a light source looks. Color temperature refers to the actual color of a light source, not the appearance of an object beneath a light source.

Although you may think of LEDs as blue-toned lights, they actually offer color temperature customization. There is no relationship or correlation between a specific color temperature and its CRI. It’s independent of each other. Don’t assume 5000K will automatically have a better CRI than 2700K because it is a whiter light. If you want to learn more about color temperature and how it’s measured, you can do so here, but that’s all we’ll discuss for now. 

According to Rensselaer Polytechnic Institute, CRI is tested using 8 standard color swatches. The color swatches are illuminated by a standard light source and then compared to a reference light source of the corresponding color temperature. CRI is then calculated from the difference in color between the test light and the reference light.

The smaller the average difference in chromaticities, the higher the CRI. So a CRI of 100 means that the test light performed exactly the same as the reference illuminant, which is most often sunlight. Below, you can see that while 60 CRI isn’t nearly as clear and vibrant as daylight, you’re still able to discern colors and appreciate their differences.

Cri Berries

It’s likely not surprising to hear that CRI can not be assessed simply with a visual. It’s much more complicated than that. Determining CRI requires a tricky calculation and high-tech equipment that’s not in the grasp of the average Joe. Luckily manufacturers present CRI information with product details, so you don’t have to worry about it. 

The predefined color samples used to calculate CRI are often called ‘Ra,’ which stands for ‘rendering average.’ The scale actually contains 15 colors, but the only instances actually used to calculate CRI are R1 to R8.

Rare Cri

You’ll notice that the first 8 samples are unsaturated, pastel colors. This presents many problems and offers the only real criticism of CRI. Pastels are soft colors and don’t represent a wide spectrum of colors. As a result, there has been an industry shift towards using the extended ‘Re’ scale, which calculates CRI using all 15 color samples.

Why Is CRI Important When Selecting LED Lighting?

Now that you know what CRI is, you may be wondering why it is so important to lighting. A survey conducted by the National Lighting Product Information Program found that industry professionals regard CRI as one of the most important considerations when choosing lighting. In this study, CRI received an average usefulness score of 3.5, compared to 3.2 for CCT, 3.1 for lamp type, and 1.9 for the brand name. We couldn’t agree more. There is an abrupt difference between high and low CRI lighting. And, although CRI isn’t calculated by eyesight, our eyes can perceive the drastic differences between lights that rank highly and lowly. 

LEDs with high CRI ratings will render colors accurately, which helps the eye discern different textures, fine details, and colors. A light with higher CRI also has a flattering effect on people, making their hair lustrous and skin look rich and healthy. High CRI LEDs are valuable in a variety of different settings. In grocery stores, for example, fruit and vegetables will look juicier and more appetizing when displayed under high CRI lights. And, in hospitals, where accurate color rendering is critical for reading test results and performing surgery, high CRI lights are absolutely essential.  

Conversely, LEDs with low CRI ratings will make things appear dull and lifeless, which is never needed. However, that doesn’t mean that each and every light needs to be 100 CRI. In fact, there are many instances where a lower CRI light will perform just as well.

What Is The Right CRI?

Every setting is different, and in some instances accurate color perception is extremely important. However, as a general rule of thumb, you should elect for a minimum CRI of 70. The closer to 100 the better, but lights of a higher CRI are more expensive, and if you can’t work 100 CRI LEDs into your budget, lower ones will certainly get you by. 

As previously mentioned, CRI is measured on a numeric scale of 1 to 100 with sunlight being 100. And even though they aren’t the peak of lighting, CRI scores in the 90s are still exceptional. They show colors almost as accurately as daylight, and the minor discrepancies that they do have will not register with the human eye. 

light bulbs cri

A CRI of 90 or higher is recommended for hospitals, museums, print studios, retail shops, and other settings where color differentiation is essential. Scores of 80 are also useful in many places that require softer or more ambient lighting, like spas or boutiques. As CRI drops below 70 however, the difference in color will become more evident to the human eye.

Is 70 CRI bad? Absolutely not. It’s actually preferable to install 70 CRI lighting in many industrial and commercial applications. The light source, even at CRI 70, is higher than most traditional light sources it replaces. And, Low CRI bulbs aren’t entirely invaluable either. In fact, they’re even desirable in some instances, such as on movie sets or at horror attractions.

Incandescent vs LED vs Fluorescent: Which Has Better CRI?

 

Type of Bulb

Average CRI

Incandescent

100

Fluorescent

50 to 80

LED

90

By now, we know that all light bulbs are not created equal. LEDs are more energy-efficient and offer a greater range of customization options than more traditional options like metal halide or fluorescent lights. So what does this mean when it comes to CRI?

Once upon a time, CRI was seen as an unimportant aspect of lighting. You get what you get kind of thing. This is because traditional incandescent bulbs were popular, which are well known for having a high CRI. So there was no need to worry about CRI. But incandescent bulbs have many drawbacks, some of which include large energy draws and a short lifespan. 

Fluorescent bulbs may seem like an attractive option as opposed to incandescent bulbs, due to the lack of heat they give off. But the CRI of a fluorescent varies from bulb to bulb and can be anywhere from 50 to 85. The same was once true of LEDs. In the past, LEDs were typically known to have poor CRIs. But as technology has evolved, LEDs have become better at color rendering than ever. Nowadays, most LEDs have an average CRI of 90.

With LEDs, ensuring that you have an appropriate CRI is as simple as reading the manufacturer’s info. So, the benefits LEDs have quickly put incandescent and fluorescent bulbs out of favor. Despite this, it’s worth noting that most LEDs have trouble at the infrared R9 end of the spectrum. An LED with an overall CRI of 95 could have an R9 value of 30. So if you’re concerned about R9 scores, just make sure that you purchase an LED with an appropriate CRI rating.

 

Color Rendering Index (CRI)

Typical Application

20 to 40

These lights are used in areas where color rendering is not important at all and a noticeable distortion of colors is acceptable.

40 to 60

These lights are used in areas where color rendering is not very important but a noticeable distortion of colors is not acceptable.

60 to 80

These lights are used in areas where moderate color rendering is needed. Practical applications include shop lights, warehouses, gymnasiums and parking lots.

80 to 90

These lights are used in areas where accurate color judgments are crucial or good color rendering is needed for purposes of appearance.

Above 90

These lights are used in areas where accurate color rendering is vital.

 

Last Updated: 11/24/2020
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