Calculating Color Differences in CIELAB: ΔE and Components (Part 4)

In CIELAB, the difference between two colors can be described as the distance between their coordinates in three-dimensional space. This makes it possible to quantify and objectively assess color differences. In this article, it is explained how color differences are calculated and interpreted in the context of quality control.

Components of Color Difference

A color difference is always determined between a standard and a batch. The differences are expressed as Delta values (Δ):

• ΔL* — difference in lightness
• Δa* — difference on the red–green axis
• Δb* — difference on the yellow–blue axis

Conventions:

• always batch minus standard for direction
• color difference is calculated in three dimensions

The total distance between both colors — the total color difference — is given by:

ΔEab = √(ΔL² + Δa² + Δb²)

In addition to Δa* and Δb*, the difference can also be expressed in terms of chroma and hue:

• ΔC* — difference in saturation
• ΔH* — difference in hue

This can help in control processes to diagnose errors faster.

Interpretation of Color Differences

The table below gives the meaning of the delta values. The differences are always defined as: batch minus standard.

| Difference | Interpretation | | ---------- | ----------------------- | | ΔL* > 0 | batch is lighter | | ΔL* < 0 | batch is darker | | Δa* > 0 | batch is redder | | Δa* < 0 | batch is greener | | Δb* > 0 | batch is more yellow | | Δb* < 0 | batch is bluer | | ΔC* > 0 | batch is more saturated | | ΔC* < 0 | batch is less saturated |

These values are used to define acceptance and rejection limits, based on historical performance and visual assessments.

Limitations of ΔE*ab

Although ΔE is a useful single number, it has limitations:

• it gives no direction of the difference
• it is not perceptually uniform (ΔE = 1 is visible for neutral colors, but barely for highly saturated greens)
• tolerance determination must always be validated per product group and material

Therefore, in modern quality control, more advanced color difference formulas such as ΔE94 or ΔE00 are often used, which better match human perception.

Practical Application in Quality Control

ΔE values are used to:

• define acceptance criteria (e.g., ΔE < 1.0 for premium products)
• monitor and release production batches
• signal and correct color deviations
• qualify suppliers on color consistency

By systematically working with CIELAB, organizations can objectively assure color quality and support discussions about color differences with measurable data.

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Questions about color differences or quality control? Contact us at info@kleurinstituut.nl or call +31 (0)70 364 98 02.