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For practitioners of high color rendering index cold light sources, the color rendering index (CRI) is a commonly used term. People often see CRI values in the data of light sources and know that it reflects the quality of the light source in terms of color rendering. However, what is its actual meaning? The CRI value helps people determine which light source should be used in a lighting device, The higher the CRI value, the better. The International Commission on Illumination (CIE) defines color rendering as the effect of a light source on the color appearance of an object compared to a standard reference light source.

Although these color samples are carefully specified, it is important to understand that the CRI value of the high rendering index cold light source is completely derived through calculation. There is no need to use a real light source to illuminate the real color sample. What people need to do is to compare the measured light source spectrum with the specified color sample spectrum, and then derive and calculate the CRI value through mathematical analysis. Therefore, the measurement of CRI value is quantitative and objective, and it is by no means a subjective measurement (subjective measurement relies solely on a trained observer to determine which light source has better color rendering). The comparison based on color perception is also meaningful, provided that the color temperature of the measured light source and the reference light source must be the same. For example, attempting to compare the appearance differences between two identical color samples illuminated by a warm white light source with a color temperature of 2900 K and a cool white light source (daylight) with a color temperature of 5600 K is a complete waste of time. They must look different. Therefore, the first step is to calculate the correlated color temperature (CCT) of the measured light source based on its spectrum. Once this color temperature is obtained, another reference light source with the same color temperature can be created through mathematical methods. For the measured light source with a color temperature below 5000 K, a blackbody (Planck) radiator should be selected as the reference light source; For the tested light source with a color temperature higher than 5000 K for high rendering index cold light sources, the reference light source is selected as CIE standard illumination body D. Now we can combine the spectrum of the reference light source with each color sample to generate an ideal set of reference colors

CRI is not a perfect measurement standard, in fact, it only reflects the color rendering of a light source for a small segment of medium saturation color, and the color point of the light source should preferably be close to the blackbody radiation trajectory, and the color temperature of the light source should neither be too high nor too low. In addition, CRI is not a universally applicable measurement standard. Although the CRI value of incandescent lamps is ideally 100, if people try to identify different deep blue colors, they will know that choosing incandescent lamps is very undesirable.

Energy distribution of spectral color temperature

The proper use of light is both a science and an art. Lighting can be simple illumination or create a certain atmosphere effect. Most people only use light for illumination, but new LED technology can make dull spaces come alive. With the emergence of high-power light-emitting LEDs and various high color quality LED lights, new technologies for obtaining high-quality LED light sources have also been introduced into the market. The different manifestations of light sources lie in how they present the colors of different objects and how they help people perceive different colors. Everyone's vision is different, so their understanding of colors can be subjective. However, as people age, their retina and cornea may be damaged to some extent, and their sensitivity to color may decrease. As a result, the differences in color understanding will be magnified, making colors less bright and color contrast less pronounced. But excellent product specifications can provide a more objective basis for comparison.