Understanding Color Rendering Index (CRI) and Why It Matters

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Understanding Color Rendering Index (CRI) and Why It Matters

The International Commission on Illumination offers an authorized definition of CRI, which refers to the Color Rendering Index. Instead of assessing the color of the light source—which is determined by color temperature—CRI is an index that quantifies how well a light source renders the color of an item. A light source’s color reproduction accuracy, or CRI, is measured in percentages between 0 and 100. Natural light is a typical reference light source to compare and measure the CRI of certain light source. LED lights typically have a CRI value of 80 to 95. LED lights that have a CRI of more than 90 are regarded as exceptional and offer superior color reproduction.

How to measure color rendering index?

  1. Choose standard color samples that accurately depict the hues of everyday items like skin, plants, and so on.
  2. Light source irradiation: Illuminate the light source to be examined on these color samples, and then analyze the spectral distribution of the reflected light.
  3. Reference light source: Pick a light source that has the same color temperature as the reference. If the color temperature of the light source to be examined is less than 5000K, the reference light source is blackbody radiation. If the color temperature exceeds 5000K, the CIE standard light source D will be used. This light source is similar to daylight.
  4. Spectrum comparison: For each color sample, compare the lighting effects of the test and reference light sources.
  5. Determine the color reproduction index. Utilize a certain calculation technique to determine the color difference of each color specimen under these two lighting circumstances.
  6. Average Color Difference: Generally speaking, the CRI of the light source is the average color difference of all test color samples.
    Nevertheless, CRI has certain drawbacks because of its small sample size for testing colors and disregard for how brightness affects color. CIE has developed TM-30-15 (Technical Memorandum 30-15), the most recent light source color quality evaluation method. This method provides a more complete and accurate light source color characterization than standard CRI.

What is the CRI of different lights?

Incandescent lights: Some incandescent bulbs have a CRI of up to 100, which is extremely high. This is so because incandescent lights have a spectrum that is comparatively continuous and capable of faithfully reproducing a wide range of colors.
LED lights: The CRI of LED lighting typically ranges from 80 to 95. While low-quality LED lights may not perform well on some colors, high-quality LED light designs can achieve color reproduction that is similar to natural light.
Fluorescent lights: Generally speaking, fluorescent lights have a CRI of about 70. Fluorescent lights may not work well in some colors and have a relatively discontinuous spectrum.
High-pressure sodium lamps typically have a CRI of between 20 and 40. It has a comparatively narrow spectrum output and is usually used for outdoor lighting like street lights.
Metal halide lamps: Depending on the particular bulb and production method, their CRI can range from 60 to 90.


Why is the color rendering index important?

Color identification: A high-CRI light source can more accurately restore the color of an object, making it appear more vibrant and closer to its actual color in the sun. This is especially crucial in settings like art galleries, printing companies, retail stores, and hospitals where precise color perception is necessary.
Visual experience: High CRI lighting can increase people’s comfort while also improving their work efficiency and satisfaction. For instance, high-CRI lighting fixtures at home can enhance the attractive appearance of food and decoration.
Biorhythms: Proper lighting influences not only how we see color but also our biological rhythms, sleep patterns, and overall wellness. High-CRI light sources support the maintenance of regular biological rhythms by being typically closer to the natural spectrum.

How do you choose color rendering index?

The needed CRI when buying LED lights varies depending on the intended application of the light. The following are some general suggestions for CRI in various applications:
Home: A CRI above 80 can suit the majority of needs and can more accurately reflect the color of object.
Working environments: offices and conference rooms often require a CRI of 80 to 90, as color authenticity is not the most important feature in these settings.
Industrial and technical fields: Lighting with a high CRI value—typically above 90 or even close to 100—is necessary for those industries that have rigorous regulations for color discrimination, such as the printing industry, medical facilities, and professional photography.
Outdoor lighting: Street lighting, security lighting, and other outdoor lighting typically do not have strict CRI criteria because their primary function is to give enough brightness to allow cars and pedestrians to see the road ahead clearly, not to restore color. Casyoo offers LED outdoor lights with a suitable CRI for each application.


LED lights have relatively high CRI and can reflect the real colors of objects. They are suitable for the majority of various applications. While choosing the CRI for your light fixtures, you can think about whether displaying the original colors is one of the important requirements for your settings. You can get in touch with us whenever you don’t know how to decide the color rendering index for your lights!

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Victor Guo

Victor Guo

Lead electrical engineer with 17+ years of experience designing electrical street lighting systems, monitoring electrical-related work at site, and discussing proposal and lighting implementation options. Bachelor’s degree in electrical engineering. Knowledgeable in LED lighting design, project management, safety and compliance.
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