What is CRI? Understanding the Color Rendering Index

When it comes to choosing lighting, there are several factors to consider. One crucial aspect that is frequently overlooked is the Color Rendering Index. Let’s take a look at CRI and why it is essential to consider when choosing your lighting.

The Color Rendering Index, or CRI, measures how accurately a light source shows the true colors of an object. It is measured on a scale from 0 to 100, with 100 indicating perfect color rendering matching the spectrum of natural sunlight. A high or ultra-high CRI value means that the light source provides an accurate representation of colors, while a low CRI value indicates a less accurate rendering. Color accuracy is important for certain applications, such as portrait studios, retail stores, hospitals, medical and commercial offices, display cases, and warehouses, where telling the difference between similar colors is crucial.

The color rendering index measures how closely an artificial light source's spectrum matches that of natural sunlight. Natural sunlight contains a broad spectrum of wavelengths, allowing us to see colors in their truest form. An artificial light source with a higher CRI will have a spectrum closely resembling natural sunlight, ensuring that colors appear true to life. In contrast, an artificial light source with lower CRI values may have gaps or spikes in its spectrum (usually around the wavelengths emitting red), leading to inaccurate perceptions. The spectral graph below can be helpful in understanding the advantages of high-CRI light sources.

Lights with a high CRI are also helpful for individuals with light sensitivity. As the color rendering index improves, the light spectrum expands, showing more red variations decreasing the blues range. A higher CRI can make a light more visually comforting.

Measuring CRI involves comparing the chromaticity, or the quality of a color measuring purity and wavelength, of an artificial light to that of a reference light. Reference lights are chosen based on the correlated color temperature (CCT) of the light that is being tested. For a light with a CCT of less than 5000K, the reference light is a black body radiator. If the CCT is greater than 5000K, then the reference is daylight. 

A “standard observer,” or software modeling the color response of the human eye, observes artificial light projected onto various color swatches. The first 8 “R” values of the “Ra” system (R1–R8) are most commonly used for color rendering tests, but other Ra values may be used for more in-depth calculations. An "R" score is then determined for each color sample by calculating the difference in reflected color between the artificial light and the predetermined reference light measurements. A formula computes an average of these R values to evaluate a light source's overall CRI.

The recommended CRI rating for any given space varies based on the purpose and activities taking place.

• Living Spaces: A CRI of 80+ is recommended to create a warm and inviting atmosphere while accurately rendering colors.
• Offices: Office environments benefit from a CRI of 80+ to boost productivity, reduce eye strain, and enhance concentration.
• Art Galleries and Museums: To showcase artwork in its truest form, lighting with a 90+ CRI is commonly used.
• Retail Spaces: Retailers often opt for 90+ CRI to make products look appealing and true to color.
• Photography studios*: Photography and video studios should use 90+ CRI lights to ensure minimal color correction is required during post-production.

*While CRI is the most commonly used metric to determine color rendering based on human eye perception, it fails to account for how camera equipment detects color. For broadcast and film applications, pay attention to the TLCI, or Television Lighting Consistency Index, measurements instead.

We sell a variety of 80+ CRI downlights, light bulbs, UFO high bays, linear high bays, and can lights. We also carry a selection of high CRI LED light strips with 90+ CRI and a brand-new line of commercial downlights with an ultra-high 95+ CRI.

You should choose ultra-high CRI lights when you want objects to appear as they do in natural sunlight. An ultra-high CRI light produces a wavelength spectrum incredibly similar to that of natural light, ensuring near-perfect color rendering. These lights are best used for illuminating art galleries, retail spaces, display cases, and museums where exact chromaticity is essential. Our ultra-high CRI commercial recessed downlights have a 95+ CRI and are perfect for commercial spaces that require a high level of color rendering and high-quality lighting.