UNDERSTANDING LAB COLOUR VALUES & DE
CIE LAB Color Scale, L*A*B* Color Values & Delta E Color Difference
What Is CIE LAB?
In color measurement, the CIE Lab* (CIELAB) color space is one of the most widely used color scales. It is applied across a wide range of industries, including paints and coatings, plastics, automotive, textiles, packaging, food, and cosmetics.
The CIE Lab* color space was developed to provide a standardized color language that more closely corresponds to human perception of color. It was derived from the CIE XYZ color system, which serves as the foundation for many colorimetric calculations. While CIE XYZ is useful for representing colors mathematically, CIELAB was developed to provide a more perceptually uniform representation, making it easier to describe and quantify color differences.
Today, CIELAB is widely used in color measurement and quality control because its L*, a*, and b* coordinates provide a practical way to describe lightness and the red-green and yellow-blue characteristics of a color.
What Does L*A*B* Color Value Mean?
Color measured using the CIE Lab* color space is expressed using three coordinates—L*, a*, and b*. Each coordinate represents a different characteristic of the color:
- L* – Lightness, ranging from black to white
- a* – Position on the green-to-red axis
- b* – Position on the blue-to-yellow axis
The table below explains the interpretation, typical range, and significance of each coordinate in the CIE Lab* color space.
Color Coordinate | Representation | Range | Explanation |
L* | Black to White | 0 to 100 | 0 corresponds to Black 100 corresponds to Diffuse White |
a* | Green to Red | -128 to 127 | -128 corresponds to Green 127 corresponds to Red |
b* | Blue to Yellow | -128 to 127 | -128 corresponds to Blue 127 corresponds to Yellow |
L*A*B* Color Scale & Color Difference ΔE
Colorimeters and color spectrophotometers are instruments used to measure and compare colors objectively.
Many instruments describe a color using three values in the CIE Lab* color space:
- L* – How light or dark the color is
- a* – How green or red the color is
- b* – How blue or yellow the color is
When a sample is compared with a standard, the instrument calculates:
- ΔL* – Difference in lightness
- Δa* – Difference in green/red
- Δb* – Difference in blue/yellow
The overall difference between the two colors is called ΔE (Delta E).
The simplest formula, CIE76, calculates ΔE as the straight-line distance between the two colors in the Lab* color space:
ΔE = √[(ΔL)² + (Δa)² + (Δb*)²]**
Modern instruments may also use more advanced formulas such as CIEDE2000 (ΔE00), which better accounts for how the human eye perceives differences in lightness, chroma, and hue.
How To Perform a Color difference analysis
Using a colorimeter or color spectrophotometer, it is easy to compare two colors and determine how closely they match.
The basic process involves comparing a Sample with a Standard (reference color).
1. Select the Standard
The Standard is the desired or approved color that you want the product to match.
For example, if a customer provides an approved red color sample, that sample becomes the Standard.
2. Measure the Sample
The Sample is the actual product or material that you want to check against the Standard.
The instrument measures the color of the Sample and records its color values, such as L*, a*, and b*.
3. Compare the Results
The instrument compares the Sample with the Standard and calculates the color difference ΔE. The result indicates how closely the Sample matches the desired color.
4. Check the Tolerance
The measured color difference is compared with the acceptable tolerance specified for the product or application.
If the result is within the specified tolerance, the Sample can be accepted. If it exceeds the tolerance, the product may require adjustment or rejection.
This process provides an objective and consistent method for color quality control and batch-to-batch consistency.
The table below provides a general reference for interpreting ΔE values. Actual acceptable ΔE limits vary depending on the industry, customer requirements, and application, but the table can be used as a rough guide.
ΔE Value | Interpretation | Result |
0 – 0.5 | Very low difference that is not noticeable to the human naked eye | Acceptable in all industries |
0.5 – 1 | Minute color differences that can be noticed by trained professionals | Acceptable in most industries except high quality control requirements |
1 – 2 | Visible color difference, but not obvious | Acceptable in few industries, but rejected in most industries |
Above 2 | Obvious color difference | Rejected in almost all industries |
Color Measurement Consultation
Looking for a colorimeter or color spectrophotometer to measure color using the CIE Lab color scale* and evaluate ΔE (color difference)?
Agaram Industries is an authorized distributor of 3nh Technology color measurement instruments in India. We offer color measurement solutions for a wide range of industrial applications.
To discuss your requirements or request a quotation and pricing, fill out the enquiry form or contact us at sales@agaramindia.com.
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