Development of Color Difference Formula ΔE*ab , ΔE*94 and ΔE*00
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发表时间：2018-11-06
Recently, we get customer inquiry for measuring CIE-lab and Delta E*00. Today we will introduce the development of color difference formulaΔE*00, ΔE*94 and ΔE*00.
Firstly, let us introduce some definition for CIE, ΔE*ab, ΔE*94 and ΔE*00.
1. What is CIE-lab and ΔE*ab?
CIE is the short name of The International Commission on Illumination. In 1976, it introduced the color space CIE-lab. The meaning of Lab, please refer to the article “Do You Know the Meaning of Color Value”.
Delta-E is a single number representing the "distance" between two colors. ΔE*ab is also called ΔE*, or, inaccurately, dE*, dE, or "Delta E".
CIE-Lab and Delta E
2. What is ΔE*94?
In 1994, CIE makes improvement on how to calculateΔE*ab. The new color different formula is ΔE*94.
3. Improvement from ΔE*ab to ΔE*94.
The color difference formula of 1976 as follows
ΔE*ab
There is obviously error, because the effects of the three channels on the human eye must be different, and the effects on the human eye under different values of the same channel are not the same. The figure below shows the chromatic aberration of different regions.
In the above picture, the horizontal axis is a and the vertical axis is b, so we can see that the larger the absolute value of a and b, the larger the area of the ellipse, which indicates the low sensitivity of the human eye to high chroma. Base on the above analysis , in 1994, CIE improved the color difference formula and new formula is as follows
ΔE*94
This formula is that when the absolute values of a and b are large, the sensitivity coefficient is also pided by a large number. The values of a and b are proportional to their respective sensitivity coefficients, and the ratios are 0.045 and 0.015, respectively.
4. Improvement from ΔE*94 to ΔE*00.
In fact, this improvement is not enough. Because it can be seen from the above figure that all the ellipse points to the coordinate origin except for the blue area in the lower left corner. And for the blue area, the sensitivity of the human eye is high, that is, the tolerance for change is low. In fact, the problem of short wavelengths of blue light and the inability to produce blue light was once a problem in the industry. Therefore, in 2000, CIE improved the color difference formula again for Blue light and other issues, and it became the following form:
ΔE*00
This is the color difference formula we still use today. CHNSpec Tech is specialized on manufacturing instruments for color, gloss and haze measurement. New products for transmittance and reflectance measurement benchtop spectrophotometer, new haze meter will come out within this year. Any inquiry, you are welcome to contact us.
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