Selecting a light bulb was pretty straightforward before the advent of LED’s.
Now that energy-efficient lighting has gone mainstream, opting for the right light source can be overwhelming with so many light-related terms.
One popular word you’ll come across is the Color Rendering Index or CRI. Unfortunately, people often misunderstand this metric of color quality. Therefore, we’ve put together a guide to explain CRI and its role in lighting.
What Is Color Rendering Index (CRI)?
Color Rendering Index refers to the accuracy of light. In other words, it measures the ability of light to display an object’s color accurately upon illumination.
For example, a green apple appears green because it reflects green wavelengths while absorbing others. However, light sources do not necessarily have the same amount of green wavelength.
Hence, the green apple will reflect a different amount of green light under varying light sources – thus altering its appearance.
The CRI measures a light’s ability to display the actual colors of an object. Hence, without a sufficient CRI light source, objects may appear dull or unlike their actual color.
CRI Became Popular In the 1960s
Scientists didn’t study light accuracy well before the emergence of fluorescent lighting. That’s partly because most light sources were close to natural light.
However, when efficient lighting technologies like Sodium lamps and fluorescents surfaced, people raised concerns about the accuracy of light illumination.
This kindled the interest in studying lighting accuracy in mid 20th century. Lighting experts began to explore different artificial light sources to understand their color accuracy.
One prominent organization that conducted the research was International Commission on Illumination (CIE). The organization started its work in the 1960s to establish Color Rendering Index measurement standards.
This led to the birth of the CRI measuring method, which became the global industry standard for measuring the accuracy of an artificial light source.
100 CRI Value Is the Highest
Color Rendering Index, like test scores, is measured on a scale. This means that a higher number implies better ability.
100 CRI score signifies the highest light accuracy of an artificial light source.
It is a convenient method to measure light’s accuracy because it is written as a single quantified number.
CRI values of 95 or above are considered among the best. However, those around 85 and below are considered inaccurate and hence very low quality.
CRI Is Perfect for Measuring Artificial Light Sources
Generally, we’re concerned about the color accuracy of artificial sources like fluorescent or LED lighting.
Why? Because a natural light source is perfect. In fact, artificial light sources are compared to our natural light source the Sun to determine their accuracy.
CRI Compares the Reflected Color of an Object Under Artificial Light Source
An artificial light source doesn’t produce the same color in an object as natural daylight would do.
Say you place a red object in an LED light of 5000K CCT (Correlated Color Temperature). It may display a different red color in the natural light (sun).
Wondering why? It’s because LED lights may have different spectral compositions compared to natural light – even if it’s the same 5000K.
Hence, the red object doesn’t have the same bright red appearance as in the natural light source.
Color Rendering Index (CRI) is thus used to measure the accuracy of an object’s color when placed under a light source.
Color Rendering Index (CRI) Ratings
Different CRI ranges can help determine the optimal range when purchasing LED lights. We recommend choosing a light with a CRI of 95 or above. A Color Rendering Index of 85 is poor. And, anything below that isn’t recommended.
Here’s a brief explanation of different CRI ranges.
Great: CRI 95-100
CRI falling on a 95-100 scale displays the truest colors. It breathes life into artwork, and depicts accurate object colors.
Most Hollywood production sets, art galleries, and premium retail stores use lights with maximum CRI to display colors brightly.
Average: CRI 85-90
Not comparable to the former, but a CRI of 85-90 is considered acceptable because it renders some colors well. It is acceptable for most commercial applications. However, the objects might not appear fully saturated as in the former CRI ratings. So it’s not recommended for artists or any serious users.
Poor: CRI Below 85
Lighting below 80 CRI has low-quality color rendering. Objects under CRI below 85 appear dull and desaturated. This means you’ll struggle to differentiate between colors that appear alike.
How to Measure CRI
CRI is measured by algorithmic calculations when the light source spectrum is measured.
To begin with, you must first determine the light source’s color temperature (Kelvin). This helps select the accurate daylight spectrum for comparison.
Then, the light source must be reflected onto several color swatches called Test Color Samples (TCS). You’ll then compare the reflected colors and determine the R score for each color swatch.
The “R” value of each color signifies the ability of the light source to reproduce a specific color accurately. So, to determine the overall CRI ability of a light source across several colors, the Color Rendering Index formula considers an average of R values.
How many R values will you average is something that depends on the CRI definition you’ll consider – general R1 to R8 or extended R1 to R15!
The Importance of Color Rendering Index
CRI plays a vital role in determining the performance of an artificial light source. Buyers have gradually acknowledged the advantages of purchasing high-CRI lighting for arts and crafts, workplace productivity and commercial environment efficiency.
Here’s why an optimal Color Rendering Index rating is crucial in everyday life.
Arts and Craftmanship
The optimal Color Rendering Index is a key element to every photo studio, workshop. Even a desk to practice a hobby, a craft or a DIY project benefit from a high CRI light because when you have selected a color you want to make sure the render is as accurate as possible. You don’t want a low CRI Led lamp be responsible to a poor choose of colors or any mistakes.
Commercial Use and Productivity
Likewise, high Color Rendering Index is also preferred among customers and retail outlet owners. The ability of light to display accurate colors enables commercial owners to make buildings visually appealing.
Likewise, consumers prefer visiting shops with better CRI lighting to accurately view products they intend to purchase.
Increased productivity is yet another perk of the high Color Rendering Index. Your workplace or study room illuminated with high CRI makes the ambience vibrant and active. Hence, it encourages you to work with more attention.
What Is Color Rendering Index (CRI)?
The CRI, or color rendering index, is a measurement of how accurately an artificial light source such as LED’s is able to render colors compared to a natural light source (The sun).
It is rated on a scale of 0-100, with higher numbers indicating a more accurate color rendering.
For a better understanding of CRI, check our article: Understanding Color Temperature Index.
How is the CRI calculated?
The CRI is calculated by comparing the colors of a test light source to a reference light source (such as natural sunlight).
The test light source is rated on how accurately it is able to render a set of standard colors compared to the reference light source.
The CRI is calculated based on a series of test colors under both the reference light source and the light source being tested. The average of these values is used to determine the overall CRI of the light source.
Tests needs to be done in a laboratory using advanced devices such as a photospectrometer or a Spectroradiometer.
Why is the CRI important?
The color rendering index CRI is important because it affects how we perceive colors in the environment.
If a light source has a low CRI (below 85), it may make certain colors appear distorted or washed out, which can affect our ability to accurately see and interpret the colors around us.
A high CRI (95+) ensures that colors are accurately rendered and allows us to see the world as it is intended to be seen.
Be aware that most manufacturer are referring to a limited CRI analyzing only 8 colors. If you want a perfect color rendering index, look for extended CRI or data sheets showing the R9 values.
Color rendering index FAQ : What is a high CRI value?
A good CRI value is generally considered to be above 90.
This means that the light source is able to accurately render most colors, with only minor deviations from the reference light source.
Please note that CRI analyses only 8 colors… missing the yellow, red colors and skin tones!
If you want a perfect color rendering look for a lamp using the extended CRI or R1-R15 values or TM30-20 index such as the Redgrass R9 desk lamp. Of course, the values should be as close as possible to the maximum, generally 100.
How do I know a light source has a high CRI?
To choose a light source with a high CRI, you can look for a light source that specifically advertises a high CRI value. 95+ for example.
You can also look for light sources that are designed to closely mimic the spectrum of natural sunlight, as this can help to ensure a high CRI.
You can also look for a more accurate index. CRI is focusing on only 8 colors. If you truly want the best color rendering possible you should look for info such as extended CRI or R1-R15 values or TM30-20 index.
Finally, you can also consult with a lighting expert or professional to help you choose a light source with a high CRI for your specific needs.
What is the difference between CRI and Color Temperature?
CRI (Color Rendering Index) and color temperature are two different ways of measuring and specifying the color of light.
CRI is a measure of how accurately a light source renders the colors of objects compared to a reference light source. It is expressed as a number on a scale from 0 to 100, with higher numbers indicating better color rendering.
A CRI of 100 means that the light source renders colors perfectly,(like the sun) while a CRI of 85 or lower may result in colors appearing distorted or unnatural.
Color temperature, on the other hand, is a measure of the hue of a light source, with higher color temperatures corresponding to a more blue or cool hue, and lower color temperatures corresponding to a more red or warm hue.
Color temperature is typically measured in degrees Kelvin (K). For example, a light source with a color temperature of 2700K would be considered warm, while a light source with a color temperature of 6500K would be considered cool. A color temperature of 5000K would be considered as a neutral white.
In general, CRI is more important for applications where accurate color rendering is critical, such as painting, drawing or museum.
This explains why artists and photographers use a color checker (a palette with standardized colors) to determine the color rendering (CRI) quality.
Color temperature, on the other hand, is more important for applications where the mood or atmosphere of a space is important, such as in restaurants or residential settings.
Color rendering index FAQ: Tips
CRI, extended CRI, R1-R15 value, TM30-20 values are an important factor to consider when choosing lighting for applications where accurate color rendering is important, such as drawing, painting, miniature painting, tattoo art and photography studios.
It is also an important consideration for home lighting, as it can affect the appearance of skin tones and the overall appearance of rooms and spaces.
It is, by far, the most important value when selecting a LED light or a desk lamp.
Conclusion
A tech-savvy person would want to check various light metrics for obvious reasons. Knowing different light-related terms helps you purchase the most accurate lighting for indoor and commercial spaces.
Color Rendering Index (CRI) is yet another value that breathes life into colors illuminated by a light source. Ensure to buy a light with a high CRI rating to enjoy optimal color quality.
Want to know more? Check our FAQ on CRI
Redgrass R9 Desk Lamp, with a CRI of 98, offers the ultimate light experience by displaying accurate object colors. The high CRI rating of the lamp is as accurate as daylight (100 CRI).