{"id":4920,"date":"2022-12-06T15:29:00","date_gmt":"2022-12-06T22:29:00","guid":{"rendered":"https:\/\/www.alconlighting.com\/blog\/?p=4920"},"modified":"2023-03-02T15:01:37","modified_gmt":"2023-03-02T22:01:37","slug":"color-rendering-index-cri","status":"publish","type":"post","link":"https:\/\/www.alconlighting.com\/blog\/lighting-design\/color-rendering-index-cri\/","title":{"rendered":"True Colors: What is Color Rendering Index (CRI)?"},"content":{"rendered":"\n

If you\u2019ve bought clothing in a store only to find out that the color looks different under natural light, the store\u2019s lighting may be the reason. More specifically, poor color rendering of the lighting.<\/p>\n\n\n\n

Color rendering is the ability of a light source to accurately reveal the color of an object. The most common measure of color rendering is the Color Rendering Index (CRI).<\/p>\n\n\n\n

Sunlight shows the true colors of an object and, therefore, has a perfect CRI of 100. It\u2019s the natural light standard against which all other light sources are compared when calculating CRI. The color of clothing in the store, food on the kitchen counter, even your skin, will look different depending on the light that\u2019s illuminating it.<\/p>\n\n\n\n

Difference between CCT and CRI<\/h2>\n\n\n\n

CRI should not be confused with correlated color temperature (CCT). While color temperature can vary throughout the day, CRI doesn’t change.<\/p>\n\n\n\n

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The CCT of sunlight varies throughout the day and in different weather conditions. You can also see how various light sources compare <\/em><\/center><\/span><\/figcaption><\/figure>\n\n\n\n

A Deeper Look at CRI in Commercial Applications<\/h2>\n\n\n\n

A CRI of 90 means that the artificial light source is replicating roughly 90 percent of the visible color spectrum that the sun would produce on the same color.<\/p>\n\n\n\n

Commercial applications that may require 90+ CRI lighting include art galleries, museums, retail outlets, hospitality and medical buildings. <\/p>\n\n\n\n

In the home, lighting with a high CRI rating may be used in areas where people apply makeup, or for work where color is important like design and construction. <\/p>\n\n\n\n

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A comparison of what colors look like under different CRI ratings<\/em><\/center><\/span><\/figcaption><\/figure>\n\n\n\n

How is CRI Measured?<\/h2>\n\n\n\n

The traditional CRI metric is based on a set of eight reference colors (see figure Color Rendering Scales below). Formal measurement of CRI is done in a lighting laboratory, most often as part of the larger process of testing and certifying a product.<\/p>\n\n\n\n

The light source being tested is directed onto the reference colors and its color rendering performance is measured by a spectrophotometer, a spectrophotometer is an instrument that measures the amount of photons (the intensity of light) absorbed after it passes through sample solution. Each of the eight results is then compared with the benchmark (the reference colors as measured in sunlight). <\/p>\n\n\n\n

For each of the eight colors, the difference in performance between the benchmark and the tested light source is calculated and given as a percentage. The eight values are then averaged to give an overall CRI rating.<\/p>\n\n\n\n

Light Sources and CRI<\/h2>\n\n\n\n

Incandescent and halogen light sources both get high (90+) CRI ratings. The light from fluorescent<\/a> and other discharge lamps is composed of a limited range of wavelengths therefore these light sources do not get a high CRI rating. <\/p>\n\n\n\n

Red tones are not well-represented in the standard Color Rendering Index. Accordingly, a light source that renders reds poorly may still have a high CRI rating; and because a CRI rating averages eight colors, there may be slight performance variation across the spectrum, and a product may still receive a high CRI rating.<\/p>\n\n\n\n

It is widely acknowledged that the eight-color CRI metric is limited. So, in recent years, an extended CRI has been used with 15 reference colors. <\/p>\n\n\n\n

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The standard CRI ratings measure color rendering accuracy using eight colors. The extended rating adds an additional seven colors to the scale, including saturated red.<\/em><\/center><\/span><\/figcaption><\/figure>\n\n\n\n

What CRI Can’t Do<\/h3>\n\n\n\n