What is CRI? The practical guide to Color Rendering Index

color rendering index
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What is CRI?

Color rendering index (CRI) refers to the accuracy of the true color of the light source displaying objects, people, and the surrounding environment.

1. Color rendering index (CRI) value
Its measure is that the higher the number, the stronger the ability, the highest is 100. A CRI value greater than or equal to 90 is considered Excellent, a CRI score of 60-85 is Good, and a score of less than 55 is generally considered poor.

2. Color rendering index (CRI) is used to measure artificial light sources.
In most cases, according to the Color Temperature (CCT), you can choose to compare with daylight or incandescent lamps to understand the color quality of LED fixtures. The CRI standard stipulates that the daylight spectrum is used for color temperatures of 5000K and higher, but the Planckian radiation spectrum is used for color temperatures below 5000K.
Note: The daylight spectrum is based on the color temperature of the LED to simulate the corresponding natural light of the sun; the Planckian radiation spectrum can be regarded as the light source of incandescent lamps and halogen lamps.

3. Color rendering index (CRI) measures and compares the reflected color of an object under artificial lighting.
The artificial light source and daylight or incandescent lamp are shined on a series of test color samples (TCS), and the reflected color is measured. Finally, take the average of all the reflection colors "R" (the reflection colors maybe 8 or 15 pcs), which is defined as the CRI of the light source.

test color samples

Image source

When discussing generic CRI, it is best to use the term "CRI (Ra)" or generic CRI (R1-R8). When discussing extended CRI, use the terms "CRI(e)", "Re" or extended CRI (R1-R15). Please keep in mind that XSY Lighting products clearly indicate CRI(Ra) when describing CRI.

According to the experiment, it is known that the color of the light source with a CRI close to 100 displays a color very similar to the way that the reference light displays the same color, so it is said that the CRI number is also higher, the stronger the ability.

What is a high CRI LED lighting?

Use different CRI (Ra) LED lights to illuminate the same object. As shown in the figure, the apparently rendered colors with low CRI on the left are not as good as those with high CRI on the right. When the CRI of an LED fixture exceeds 90, it is classified as a high CRI LED.

cri 80 vs cri 90

High CRI products: Star4 60w, Diamond, Sunrise4

Choose the right CRI

  1. For most indoor, industrial and commercial lighting, 80 CRI (Ra) is a general benchmark for acceptable color rendering. Sometimes 70 CRI (Ra) customers will also choose.
  2. When it comes to lighting areas where color accuracy is critical, such as photography studios, offices, hospitals, high-end hotels, retail stores, textile factories, printing plants, or paint shops, 90CRI (Ra) and above may be a good starting point.
  3. If your lighting area wants to show high-quality red, please pay attention to the R9 color rendering value, it can produce a strong, vibrant red.

R9 is one of the numbers of Ri refers to test color samples (TCS), which is one score in extended CRI. It is the number rates the light source’s color revealing ability towards TCS 09. And it describes the specific ability of light to accurately reproduce the red color of objects. So, generally, it is regarded as a supplement of color rendering index when evaluating a high-CRI light source.

R9 value, TCS 09, or in other words, the red color is the key color for many lighting applications, such as film and video lighting, textile printing, image printing, skin tone, medical lighting, and so on. Besides, many other objects which are not in red color, but actually consists of different colors including red color. For instance, the skin tone is impacted by the blood under the skin, which means that the skin tone also includes red color, although it looks much like close to white or light yellow. So, if the R9 value is not good enough, the skin tone under this light will be more paleness or even greenish in your eyes or cameras.

Source: Wikipedia

Conclusion

It is a trend that users and manufacturers pay attention to CRI value. We, as LED lights manufacturer have never fabricated values ​​arbitrarily. Usually, we will test the product by integrating sphere measurement to obtain real data reports. You can also contact us if you need it. As with trying to understand color temperature, the most direct way is to take a sample and observe the performance of lighting in your space.

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