I. What is Color Rendering

Color rendering refers to the ability of a light source to reproduce the true colors of objects compared to a standard light source (i.e., the degree of color fidelity of the objects). The standard light source is based on the CIE (International Commission on Illumination) standard illuminants, with natural sunlight being a typical representative.

Light sources with high color rendering have good color reproduction, and the colors of objects are closer to their natural original colors.
Light sources with low color rendering have poor color reproduction, and the color deviation of objects is more obvious.

1.1 Color rendering is divided into two types:

1.1.1 Faithful Color Rendering

Requires the use of light sources with a high color rendering index (Ra) (color rendering is optimal when the value is close to 100) to accurately present the intrinsic colors of objects.

1.1.2 Effect Color Rendering

Aims to enhance specific color performance or create a special atmosphere through additive color methods. Illumination with a low color temperature light source can make red more vibrant; illumination with a medium color temperature light source can give blue a cool feeling; illumination with a high color temperature light source makes objects appear cold.

II. What is the Impact of Color Rendering? What is its Relationship with the Color Rendering Index?

The higher the color rendering, the more realistic the colors of objects under the light; the lower the color rendering, the more obvious the color difference of objects, which not only affects color judgment but may also have adverse effects on visual health.

The color rendering index (abbreviated as CRI in English, commonly represented by the value Ra) is a general method for evaluating the color rendering of a light source. The CIE specifies 15 standard test color samples (R1-R15). In practical evaluation, the average color rendering index of the first 8 color samples is taken and recorded as the “Ra” value. The higher the color rendering index Ra, the better the color rendering of the light source. Among them, R9~R15 are called “special color rendering indices”, especially R9 (deep vivid red) and R15 (Chinese skin tone).

The International Commission on Illumination (CIE) divides the color rendering index into five grades, generally applied to:
1. A > 90 Places where precise color comparison is required.

2. B 80 – 90 Places where correct color judgment is required.

3. 60 – 80 Places where moderate color rendering is required.

4. 40 – 60 Places with lower requirements for color rendering and smaller color differences.

5. 20 – 40 Places with no specific requirements for color rendering.

III. What Color Rendering Index is Considered Up to Standard?

National standards stipulate that for rooms and places where people work or stay for a long time, the color rendering index (Ra) of the lighting source should not be less than 80. That is to say, only light sources with a color rendering index of 80 and above can restore the true colors of objects and reduce color differences.

IV. Color Rendering Indices of Common Light Sources

The theoretical color rendering index of an incandescent lamp is 100, but there are many types of incandescent lamps in real life with different applications, so the Ra values are not completely consistent and can only be said to be close to 100. Based on the spectral distribution measured by the spectroradiometer CS-2000, the color rendering indices of the following light sources can be obtained.

To test the color rendering/color rendering index of objects, professional lighting products can be used, such as the LSB-MSL26 / LSB-MSL32-IR Multispectral Light Source Box launched by Yanding for professional image quality testing. It has built-in A, H, D50, D65, D75, and daylight spectra. Its D50-D75 light sources have CRI >97, and A/Horizon light sources have CRI >95, which can simulate various environments such as daylight, fluorescent, and incandescent light.