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. 

When measuring for CRI, the artificial light is projected onto 8 specific color swatches, and the reflected colors are measured. The U.S. most commonly uses the “Ra” system, which tests R1–R8, but other countries may use different systems. An "R" score is calculated for each color sample by calculating the difference in reflected color between the reference lights and artificial light. To evaluate a light source's overall CRI, the formula computes an average of these R values. Read more about the different CRI systems here.

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.

We sell a variety of 80+ CRI downlights, light bulbs, UFO high bays, linear high bays, and can lights. We also carry ultra-high CRI light strips.