Color rendering index in lighting

2020-01-13

CRI

What is Color Rendering?

Color rendering defines how a light source renders the color of an object in the human eye compared to a high-quality reference light source (the sun). It further defines how the light source renders subtle changes in color well.

What is the Color Rendering Index?

The color rendering index (CRI) is a scale from 0 to 100. 0 is considered poor quality. 100 is considered the perfect light source. Compared to the colors that appear in daylight or a reference light source, it represents the accuracy of the light source when rendering colors.

The higher the CRI, the better the color rendering ability of the light. The colors are displayed accurately. For example, the red under CRI 90 looks clear and bright. Under the CRI 70 light source, the same red color is displayed as dark gray.

What is a good CRI score?

Light sources with a CRI of 85 to 90 are considered to have excellent color rendering. Light sources with a CRI of 90 or higher are very good. For LED light, the typical range of CRI options is 70 to 98.

70 CRI is not good? Absolutely not. It is perfectly acceptable to install 70 CRI lighting in many industrial applications. Even at CRI 70, this light source is higher than most traditional light sources it replaces.

Is 98 CRI great? Yes. But it comes at a price. Higher CRI LEDs are also more expensive. You will find high CRI LEDs in movie lights. This is to ensure that the color accuracy of the content you are shooting or watching is as perfect as possible.

How does CRI relate to color temperature?

When buying an LED bulb, you need to determine the color temperature of the bulb (what is its temperature). This is the Kelvin indicator. The typical range of LEDs is between 2700K (warm) and 6500K (cold).

Then you need to look at the CRI of the bulb. This determines the quality of the light source. There is no relationship or correlation between a particular color temperature and its CRI. They are independent of each other. Don't think that 5000K will be a better CRI than 2700K because it is white light.

How to calculate CRI?

Calculate the CRI based on the degree to which the light source renders 8 defined soft colors. In the image below, all 14 test colors are shown. The primary colors are the 8 colors shown on the left.

The artificial light is directed at the primary color sample. Measure the color of the reflection. This measure of reflected color determines how close it is to the primary color. The more accurate the original color sample is measured, the higher the CRI value.

Color rendering index application reference

Color Rendering Index (CRI)    Typical Application

20 to 40   These lights are used in areas where color rendering is not important at all and a noticeable distortion of colors is acceptable.

40 to 60   These lights are used in areas where color rendering is not very important but a noticeable distortion of colors is not acceptable.

60 to 80   These lights are used in areas where moderate color rendering is needed.

80 to 90   These lights are used in areas where accurate color judgments are crucial or good color rendering is needed for purposes of appearance.

Above 90 These lights are used in areas where accurate color rendering is vital.