What is Color Rendering Index (CRI)?
High CRI value makes true color viewing
What is CRI?
Color Rendering Index (CRI) is commonly used is widely regarded as the measurement for evaluating the color rendition ability of a light source. When looking for good lights, CRI value is a critical factor that we should consider.
A high CRI light is able to reveal the colors of objects, especially the red color. For example, a red rose under the 97 CRI light looks vivid with true colors, while under the 80 CRI light, it appears dull, fade and inaccurate in color.
Color Rendering Index (CRI) is not the parameter to be judged by looking at a light. We must look at how a light impacts the color rendition of illuminated surface. In other words, it is the parameter to judge a light’s ability to show object colors realistically or naturally.
Color is a perceptual response of human eyes, which is triggered by the spectral radiation of light source. We can see different colors is due to the different wavelengths of light. Different wavelength radiation will cause a different sense of color to human eyes. For instance, the red color in human eyes is generally caused by the wavelengths above 620nm. Blue color is generally caused by the wavelengths around 450nm.
Saturated Blue Color
Saturated Red Color
All types of light sources, such as sun, fluorescent lamps, fire as well as LED lights, have different intensity radiation in a range of wavelengths, which is called spectral power distribution (SPD). When the light sources illuminate objects, objects will absorb and reflect light radiation at the different wavelengths.
For example, a red rose will absorb the wavelength of shorter than 620nm (RED), but reflect the wavelength above. The picture below shows the color stimulus function of it, which is helpful for the understanding of the concept of color perception and color rendering difference.
80 CRI Light
98 CRI Light
As we can see in the pictures above, 97 CRI light comprises of a full range wavelength spectrum. The red rose will absorb all radiation but reflect red color radiation. In comparison, 80 CRI Light is not able to emit enough power of red color radiation, therefore, the rose is not able to reflect enough red color radiation as well. Consequently, the sense of red color is weak in human eyes’ or cameras’ perception.
Why high CRI is important?
The comparison between normal lights CRI 80 and MM's lights High CRI 97
High CRI, Ra and Re
In short, Color Rendering Index (CRI) is the criteria to describe the level of a light source’s ability to reveal the color of objects.
The most commonly used value of CRI is called Ra, which is the average value of first 8 index (R1-R8).
There is another index that people is not familiar with, which is Extend CRI (Re). It is more accurate as we can see more colors rendition performance with average value of all 15 index (R1-R15).
Color Rendering Index (CRI) is determined by the distinctions in the chromaticities of 15 CIE ISO-TCS (CIE 1995) when objects enlightened by a light source and a reference illuminant with same correlated color temperature (CCT). In short, the lower CRI value is, the smaller the differences will be. A CRI value of 100 speaks to the best performance of a light source. Low CRI value may show some colors unnatural or unreal.
Why R9 is important?
As a typical value of Ri test sample 9 (a saturated red color), it is sometimes listed seperately as a supplement vaule to general CRI (Ra).
In Particular, the special index R9 is often noticed by people who working in some specific field, such as film and video lighting, medical lighting, textile, painting etc. Because high R9 value represents much accurate color of red, which is significant for those applications.
R9 is the value breaks the limitation of average value of R1 through R8, which provides much precise reference to evaluate the light sources’ ability of the red portion visible spectrum. It is much helpful for lighting objects containing red color, such as human skin tone, red spray painting, red pigments etc.
What is High CRI FULL Spectrum ?
Objects will sometimes appear a slightly different color when illuminated with lamps of different color temperature, even if both lamps have the perfect color rendering Index.
Color Rendering Index
Why lights can get high CRI value ?
Physically, the energy of wavelength impacts the Color rendering index value directly.
Mathematically, CRI value is calculated with 15 color samples, which called TCS or Test Color Samples, with respective TCS spectrum. We make lights with full spectrum covers the area of 15 TCS spectrum as much as possible to make the color rendering index value as high as possible.