ΔE*

Delta E measures the difference between two colors in a three-dimensional color space (typically CIE Lab). It quantifies color changes based on three axes: Lightness (L*), Red-Green (a*), and Yellow-Blue (b*). This allows conservators to assess and compare how closely different colorants match, both in terms of the visual result of mixed pigments or as they degrade over time.

Understanding Color Differences

ΔL*: Shows how much lighter or darker one color is compared to the other. Positive means the second color is lighter, negative means it's darker.

Δa*: Positive means the second color is more red than the first. Negative means the second color is more green than the first.

Δb*: Positive means the second color is more yellow than the first. Negative means the second color is more blue than the first.

ΔC*: Positive means the second color is more vivid or intense. Negative means the second color is more dull or grayish.

ΔH*: Measures the difference in hue between two colors, which is a more complex calculation because it involves both the a* and b* components. In practice, ΔH* is always positive, as it represents the magnitude of the angular difference in hue.

ΔE*: A total measure of how different two colors are, combining all aspects (lightness, chroma, hue, etc.). The higher the value, the more noticeable the difference. A ΔE* of less than 2 is imperceptible to the naked eye.