Color is an important quality parameter in industries such as plastics, paints, textiles, food, cosmetics, chemicals, packaging and automotive manufacturing. Visual color assessment can be subjective because perception is influenced by lighting, the observer, surface texture and surrounding colors. Color measurement instruments provide numerical data that allow colors to be measured and compared objectively. Colorimeters and spectrophotometers are commonly used for this purpose. Instruments offered by color measurement brands such as 3NH can support parameters including CIELAB, L*a*b* and ΔE.
What Is a Color Measurement Instrument?
A color measurement instrument analyzes light reflected from a surface, or transmitted through a sample in applicable systems, and converts the result into numerical color values.
These instruments can be used for:
- product color comparison
- batch-to-batch control
- comparison with reference standards
- color tolerance evaluation
- quality control
They are particularly useful for detecting small differences that may be difficult to evaluate consistently by eye.
What Is the CIELAB Color System?
CIELAB is a widely used color space defined by the International Commission on Illumination (CIE).
Colors are represented using three primary coordinates:
L*, a* and b*
These coordinates provide a numerical description of the color.
What Does L* Mean?
L* represents lightness.
In general:
L* = 0 → Black
L* = 100 → White
Higher L* values indicate lighter colors, while lower values indicate darker colors.
What Does a* Mean?
The a* axis represents the red-green direction.
+a* → Red
−a* → Green
What Does b* Mean?
The b* axis represents the yellow-blue direction.
+b* → Yellow
−b* → Blue
This parameter can be particularly useful for monitoring yellowing or other color changes in light-colored materials.
What Are ΔL*, Δa* and Δb*?
These values describe the differences between a reference standard and a measured sample.
ΔL* indicates the lightness difference.
Δa* indicates the difference along the red-green axis.
Δb* indicates the difference along the yellow-blue axis.
Together, they help identify not only how much the color has changed but also in which direction it has shifted.
What Is ΔE?
ΔE (Delta E) expresses the overall color difference between two colors as a numerical value.
The classical CIELAB ΔE*ab (CIE76) equation is:
ΔE*ab = √[(ΔL*)² + (Δa*)² + (Δb*)²]
A smaller ΔE generally indicates closer colors, while a larger value represents a greater color difference.
However, there is no universal acceptable ΔE tolerance for every industry or product. Acceptance limits should be defined according to the application, customer requirements and ΔE formula being used.
ΔE76 vs. ΔE94 vs. ΔE00
Several formulas are available for calculating color difference, including:
- ΔE76
- ΔE94
- ΔE00 / CIEDE2000
CIE76 is the simpler mathematical model. Later formulas, particularly CIEDE2000, were developed to better account for how the human eye perceives differences in various color regions.
When comparing ΔE results, it is therefore important to know which formula was used.
Colorimeter vs. Spectrophotometer
| Feature | Colorimeter | Spectrophotometer |
|---|---|---|
| Primary purpose | Color measurement | Detailed spectral measurement |
| L*a*b* | Yes | Yes |
| ΔE | Yes | Yes |
| Spectral data | Usually limited | More comprehensive |
| Typical use | Routine color QC | Detailed color analysis and QC |
The correct instrument depends on the required accuracy, sample type and measurement information.
Why Are Illuminant and Measurement Geometry Important?
The same object can appear different under different lighting conditions.
Color measurements may therefore specify standard illuminants such as D65 or A, together with defined observer conditions.
Measurement geometry is also important. Instruments may use geometries such as d/8° or 45°/0°.
Surface gloss, texture and roughness can influence results, so measurement conditions should remain consistent when comparing samples.
Applications of 3NH Color Measurement Instruments
Depending on the model, 3NH colorimeters and spectrophotometers can be considered for applications including:
- plastics
- paints and coatings
- textiles
- packaging
- paper
- printing
- cosmetics
- food
- automotive
- chemicals
- quality-control laboratories
Important selection criteria include measurement geometry, aperture size, repeatability, illuminants, supported color spaces and ΔE formulas.
Tips for Reliable Color Measurement
For consistent results:
- Calibrate the instrument correctly.
- Keep the sample surface clean and representative.
- Select an appropriate measurement area.
- Measure the reference and sample under identical conditions.
- Use the same illuminant and observer settings.
- Take multiple measurements when necessary.
- Record the ΔE formula used.
Conclusion
Color measurement instruments replace subjective visual judgment with numerical and comparable color data.
In the CIELAB system:
L* → Lightness
a* → Red / Green
b* → Yellow / Blue
while ΔE is used to evaluate the overall color difference between two samples.
Selecting the correct instrument, measurement geometry, illuminant and color-difference formula helps achieve more reliable and repeatable color control in laboratory and industrial quality-control applications.
