Color Rendering Index: Everything You Need to Know

Do you know a simple miscalculation in the selection of the CRI value of lighting design can damage a space's overall look and feel? The Color Rendering Index (CRI) is a fundamental concept in lighting design that quantitatively measures the color accuracy of artificial lighting compared to natural light.

In this article, we jump into the complex world of CRI, its benefits, testing procedures, and applications to give you a crash course on everything you need to know about the color rendering index.

What Is a Color Rendering Index? (CRI)

The color rendering index (CRI) measures an artificial light source's ability to faithfully reproduce an object's colors compared to a natural light source.

CRI is a 1 to 100 rating that is a quick and easy means of understanding the color rendering accuracy of a light source. A CRI of 100 means the objects under an artificial light source look the same as they would under sunlight.

The unit for CRI is often listed as Ra, which stands for R average or the average color rendering capabilities.

The Commission Internationale de l'éclairage (CIE), or International Commission on Illumination, is a century-old institute setting industry standards on light measurement, including the basics of CRI ratings.

Importance of High CRI Ratings

CRI ratings serve a simple but useful purpose: represent objects, décor, people, etc., in the best light possible. Accurate reproduction of an object's appearance is a valuable tool in several industries.

Following is a short list of color-critical industries that showcase the importance of high CRI lighting.

Photography

Good lighting design and good photography go hand in hand. The quality of pictures increases exponentially with the quality of the light source.

High CRI lighting can accurately reproduce the true subject colors, especially for subjects' skin tones. Digital cameras often struggle to capture the natural skin color of people, and high CRI lighting allows photographers to capture more natural-looking images.

Good lighting leads to accurate image recreation in the camera, which leads to more accurate image displays and prints.

Low CRI lights, like fluorescent bulbs, can introduce a slight green or magenta cast to the photos. The color cast becomes a nightmare in post-processing, where an editor has to remove unwanted color hues painstakingly.

Art Galleries

A major challenge for art galleries is preserving the vision and intent of the original artist. Paintings from the last 1000 years have used several hundred materials to generate the same vibrant colors.

When artificial light interacts with the ancient paints in these historic paintings, it distills color. Showcasing paintings in natural light is also not an option, as the UV (ultraviolet) radiation from the sun causes fading and distortion.

The only solution to this complex problem is high-quality non-UV LED lighting with a general color rendering index of 90 or above. LEDs are particularly useful here as they are incredibly energy-efficient and have a low heat output.

Retail Stores

Stores run on the quality of the products and the marketing behind the products. Whether it's a grocery stand, a clothing boutique, or a furniture store, the products need to shine and look their best.

High CRI light sources make the colors pop. Bright, saturated, and colorful displays attract customers and directly result in sales. The goal of any retail business should be to emphasize the natural colors of its products and enhance its visual appeal.

Quality LED lighting has also been shown to impact the mood and temperament of customers. So, it should be no surprise that businesses prioritizing customers' visual comfort also see higher sales.

Product Development

Researching and designing a product is an incredibly challenging process. Perfecting the dimensions, specifications, and product capabilities is already very tough. Add to that accurate color representation, and you have a tremendous task.

A quality product should have a consistent color choice and material finish. Minor visual inconsistencies indicate bad product design and lead to poor brand representation.

A high CRI lets manufacturers maintain consistent color reproduction through multiple batches.

Example: Apple sells tens of millions of iPhones each year. The company must maintain accurate color representation across several factories and vendors for its millions of products. Using standard CRI (color rendering index) and CCT (color correlated temperature), lighting quality allows Apple to maintain its excellent product quality control.

Clothing Industry

Finally, the clothing industry is the biggest beneficiary of high-quality lighting. Clothing is all about making a visual statement and being your best self.

The clothing industry relies on good lighting to showcase its products and attract customers. Clothing stores put as much effort into illuminating their products as they do in making them.

While incandescent light sources were common in the old days, they have proven lacking compared to modern LED (light emitting diode) lighting. But LED lighting isn't limited to clothing stores.

Accurate LED lights are necessary for designing clothes, sourcing fabrics, and testing after-wash changes. There needs to be a standard illumination measuring system to test the color rendering of fabrics completely. Luckily, the color rendering index (CRI) ratings are just that system.

Color Rendering Index (CRI) vs. Color Correlated Temperature (CCT)

CRI and CCT are two similar but inherently different lighting quality measurement standards. These terminologies are designed so lighting manufacturers can properly describe and market their products to consumers and serve different market sections.

Color Rendering Index (CRI)

• The color rendering index is a metric for measuring a light source's ability to mimic natural sunlight.
• It has a scale ranging from 0 to 100, with 100 CRI representing the properties of natural light sources.
• CRI is primarily used in photography, retail stores, and art galleries to display an object's colors accurately.
• The color rendering index is all about accuracy and doesn't concern color temperature. A warm (lower CCT) LED light source can still have a high CRI. In such a scenario, a high CRI shows that the light source accurately displays a product as if it were under natural light during sunset.

Correlated Color Temperature (CCT)

• Correlated Color Temperature measures the color appearance of illumination by a light source.
• It is expressed in Kelvin (K) and ranges from 1,000 K to 10,000 K. With a 1000 K light source having the same temperature as a warm candle flame and a 10,000 K light source having the same light color as a clear blue sky.
• CCT describes whether a light source appears warm (lower Kelvin values) or cool (higher Kelvin values) in terms of color. For example, incandescent lamps are warm and have a lower CCT (around 2700K), while fluorescent lamps are cooler and have a higher CCT (around 5500K).
• CCT does not provide information about the color rendering properties of a light source. It only tells you the general color appearance of the light emitted by the source.

How to Measure Color Rendering Index (CRI)?

Measuring a given light source's color rendering index (CRI) involves a complex testing procedure, a good understanding of the light spectrum, and some advanced mathematics.

Luckily, we have broken down this complex process into simple, easy-to-understand, bite-sized pieces.

Step 1 - Selection of Test Colors

The CRI test uses 8 or 15 standardized test colors, including pastel tones, saturated and neutral colors. These colors represent a range of hues and saturation levels.

Most color rendering index scores are based on the eight standard color palettes, but an additional 9th color is sometimes included to measure red color recreation.

For more advanced color rendering tests, 15 palettes are used instead. The results of an 8-color test and a 15-color test for the same light source will vary quite a bit.

Step 2 - Control Test with Natural Light Source

Now that you have selected your set of test colors, 8, 9, or 15, it's time to run a control test. This basic test will act as a reference for your artificial light source.

A common reference light source is Natural daylight (Daylight Illuminant D65). The test colors are exposed to this light source, and a light measuring tool analyzes the color rendering capability of the light source.

Step 3 - Testing Color Samples

After exposing the test colors to the natural sunlight (or other control light source), a light measuring tool is used to analyze the wavelength and amplitude of the light reflected off of the samples.

Two types of tools are used to measure the color rendering results.

• Spectroradiometer: A tool with an illumination sensor and sensitive optics that can detect minor changes in the wavelength and amplitude of a light source.
• Spectrophotometer: A tool that measures the amount of photons (light packets) that pass through a sample.

The resultant light emission values are logged into a system for later comparison.

Step 4 - Testing with Artificial Light Source

Next, repeat the same testing procedure with your desired artificial lighting. Expose the set of test colors to the artificial light source and measure the results.

The light source should be stable and operate at the manufacturer-rated brightness and color temperature.

Step 5 - Taking Color Samples Again

Repeat step no. 3, and note down the results of the artificial light source.

Step 6 - Calculating Color Rendition Accuracy

Use the visible spectrum data from both light sources and compare the results. The comparison involves plotting color values in a chromaticity coordinate system and matching the artificial light source results with the natural daylight results.

Each of the test colors will be compared individually. If you're using an 8-color set sample, you will have eight different comparison values, listed from R1 to R8.

Step 7 - Averaging the Results

Now that we have the comparison results from all eight test colors, we can calculate the average color rendering value Ra.

Ra is the average of all colors, from R1 to R8 (or R15).

Step 8 - Final Color Rendering Index (CRI) Score

Now, we refine all the calculations into one single number on a scale of 0 to 100, with 100 indicating perfect color rendering (i.e., the light source accurately reproduces all colors).

Which CRI Ranges to Use？

The color rendering index (CRI) is commonly broken down into five categories based on application. Manufacturing high-CRI LED lights is expensive; not all businesses benefit from 90+ CRI fixtures.

The lowest quality light sources fall under category 4, which comprises fixtures rated 20 to 39 Ra. The second lowest is category 3, with 40-59 Ra fixtures. Categories 3 and 4 have such poor color rendering capabilities that they can only be deployed in street lamps and warehouses.

Moving ahead, we have category two light fixtures, and these units have an acceptable color rendering score of 60-79 Ra. Anything above 70 Ra is considered good quality lighting. It is the minimum requirement of a residential building that ensures residence comfort.

Next, we have the top two categories, 1A and 1B. For color-sensitive applications, like product marketing and paint manufacturing, 1B is recommended. It ranges from form 80-89 Ra.

Finally, we have the cream of the crop, the highest color rendering index category 1A. It ranges from 90-100 and is the only acceptable light source for professional color-critical applications. The fashion industry, art galleries, photography studios, and more rely on category 1A light sources for daily business operations.

Manufacturing fixtures with a CRI of less than 20 is practically impossible. Light quality would have to be abysmal for a fixture to get such a low color rendering score. Contrarily, manufacturing 100 CRI light bulbs is comparatively easy.

A Deeper Look at CRI In Commercial Application

Let's look at some specialized commercial applications of high CRI light fixtures.

1. Aquarium

The aquarium industry might seem small to outsiders, but it is a massive culture involving art, science, and architecture. Lighting an empty room is challenging enough on its own. Add lots of refractive water, a bunch of underwater decorations, and some photo-sensitive fishes, and your job gets much tougher.

• Better Color Reproduction: High CRI light sources are highly recommended for aquariums and similar water lighting situations. Fixtures rated 90+ Ra reproduce the natural colors of underwater plants and fish more accurately, making your aquarium pop from its surroundings.
• Health and Safety of Fish: Research shows fish are more sensitive to light at higher wavelengths. Thus, we can safely say that high CRI lighting positively affects your fish's mental and physical health.

2. Medical Applications

High CRI (Color Rendering Index) lighting plays a critical role in medical imaging applications, where color accuracy and lighting quality contribute to accurate diagnosis, visualization, and patient care.

Following are just some common medical industry applications of high CRI lighting.

• Radiology and Diagnostic Imaging: High-quality lighting with good CRI is essential in radiology and diagnostic imaging rooms where X-rays, CT scans, MRIs, and other medical images are analyzed. Accurate color representation helps healthcare professionals distinguish subtle image variations, leading to more accurate diagnoses.
• Surgical Suites: In surgical suites, visual clarity and color accuracy during procedures is a necessity. Surgeons and medical staff must accurately perceive tissues, blood, and other anatomical structures.
• Dental Clinics: High CRI lighting helps identify dental conditions, select appropriate materials, and ensure dental work quality.

• Dermatology: Dermatology is all about getting a clear picture of the human skin and assessing skin conditions, such as moles, rashes, and lesions, with precision. Proper high CRI lighting aids in diagnosing and treating skin disorders.
• Laboratories: In medical and research laboratories, high CRI lighting is essential for tasks like sample preparation, chemical analysis, and experiments. Such places deal with milligrams of materials and require good lighting design to manage sensitive materials.
• Operating Rooms: Operating rooms require high CRI lighting to give surgeons accurate color perception and visibility during procedures. This lighting is critical for the success and safety of surgical interventions.

3. Industrial Applications

High CRI (Color Rendering Index) lighting plays a significant role in factories and other industrial spaces' safety, productivity, and efficiency.

Following are some common industrial applications that benefit from high CRI lighting.

• Quality Control and Inspection: Accurate color representation enables workers to identify defects, inconsistencies, or variations in materials and products more effectively. Take the example mentioned above of iPhone production.
• Safety and Hazardous Areas: Industrial workspaces often have hazardous materials lying around, and identifying chemicals, oil spills, and container leaks is critical to worker safety. Category 2 or higher CRI lighting is used to ensure that safety signs, emergency exits, and equipment labels are visible and identifiable.
• Painting and Coating: Production areas that deal in coloring, painting, and powder coating devices need good lighting to ensure color consistency and accuracy from product to product.
• Visual Inspections: Visual inspections in industrial settings, such as welding inspections, weld bead quality assessments, and defect identification, require high CRI lighting to enhance the visibility of details and imperfections.
• Pharmaceutical and Food Production: In the pharmaceutical and food industries, where color accuracy is essential for safety and quality, high CRI lighting helps with visual inspections, label matching, and quality control procedures.

• Cleanrooms and Laboratories: Cleanrooms and laboratories are the most heavily regulated areas. Large factories that deal with the production of microprocessors have insanely high standards for cleanliness and visibility. High-quality CRI lighting helps identify the smallest grain of unwanted dust in a cleanroom.
• Textile and Printing: Industries that involve textiles, graphic arts, and printing rely on high CRI lighting to assess colors, patterns, and print accuracy.

Light Color Rendering Index (Ra) of Common Light Fixtures

Here are typical CRI ranges for common light sources, ranging from traditional incandescent lamps to specialized xenon lamps.

Incandescent and halogen light sources generally average the highest CRI among all light sources. However, these light bulbs are also limited to warm color temperatures, and this has limited applications. This indicates that while CRI is a good measuring stick for illumination quality, it should be used with other tools like color temperature.

LED lighting has a comparatively lower average CRI. However, lighting manufacturers can use specialized techniques like adding red phosphor to the diodes to increase the CRI to 100. Again, these minor details show that a color rendering index is more complex than a simple number.

How to Choose the Right CRI Lighting

Choosing the right CRI lighting is about identifying your business needs and finding the closest matching lighting source.

Here are three steps that will help you get the best CRI lighting for your workspace.

1. Identify the Application

Quality CRI is necessary for two types of applications.

• Product Highlighting: Any sales work requires decently high CRI lighting so that their products can look the best for potential customers.
• Health and Care: Poor color rendering strains eyes and creates a generally unwelcoming atmosphere. Good CRI lights are recommended for homes, healthcare spaces, and the hospitality industry.
• Color Accuracy: Photography, product design, and art-related applications require the highest possible CRI lighting.

2. The Level of CRI Required

Now, we know the basic applications that benefit from a high CRI light source. We can talk about hard numbers.

• For product showcases, a CRI of 85 or higher is generally recommended. Fruit and Veggie stores, Clothing boutiques, and Gift shops all require good lighting for their products.
• For general indoor lighting in homes, restaurants, and other public spaces, a CRI of 75 or higher is recommended.
• For color-sensitive applications, like photo studios, product and clothing design, and medical imaging, a CRI of 95+ is recommended.

3. Define Your Budget

Finally, we have to consider the biggest deciding factor in your budget. High CRI lights are not cheap; going from 80 CRI LED lights to 90 CRI ones is a huge leap in price.

• Energy Efficiency: The initial investment cost of high CRI lighting can be offset by the energy efficiency of LED lights. This is especially true if you go from warm halogen light sources to LEDs with the same color temperature.
• Warranty & Lifespan: High CRI lights are made with special care to ensure the highest illumination quality. The higher quality of these light fixtures also results in higher lifespans.
• Budget Constraints: If your budget is tight, you can downgrade from 95 CRI lights to 80 CRI in specific applications. While not ideal, 80 is still a high CRI and will result in more accurate color renditions.

FAQs

1. What Does 80 CRI Mean?

A CRI of 80 means that objects under this light source will have 80% color accuracy compared to natural daylight.

2. What Is the Difference Between 80 CRI and 90 CRI?

90 CRI light fixtures have 90% of the color rendering accuracy of sunlight. Light fixtures with 80+ CRI are recommended for most commercial applications where color accuracy is needed. Compared, fixtures with 90+ CRI primarily focus on professional applications like photography and art galleries.

3. What Is the Difference Between CCT and CRI

CRI is the ability of an artificial light source to mimic the properties of sunlight, while CCT is a measure of the yellow and blue hues present in artificial lighting.

4. What Is the Difference Between Low CRI and High CRI?

Low CRI lights distort objects' colors by adding blue or green casts. High CRI lights represent an object's true colors as if they were under natural daylight.

5. What Is a Good Color Rendering Index?

For most applications, a CRI of 75 or above is recommended. However, a CRI of 85 or above is ideal for color-sensitive professional applications.

Conclusion

The world of CRI is complex and full of technical jargon like color rendition and light spectrum. But once you learn the basics of this lighting standard, the entire process becomes much simpler. High CRI lighting has several benefits beyond making product displays glow and pop. It helps professionals create even better products and enables businesses to create a more welcoming indoor space.

Discover the Perfect CRI Lighting for Your Business with Risun

Risun is all about matching high-quality lighting solutions with esteemed buyers. We aim to deliver cost-effective lighting solutions to our international clients with the best possible customer service. Check out our diverse catalog of indoor and commercial lighting products that cover a broad range of industries and applications.

Your business needs a partner that understands its needs and values its success. Luckily, Risun is just that partner.

Get started on your perfect CRI lighting setup today. Contact us Now!