In order to measure the difference between two colours, the difference is assigned to a distance within the colour space. In an equidistant-method colour space, the colour difference ∆E can be determined from the distance between the colour places:
ΔE = √ (L*₁-L*₂)² + (a*₁-a*₂)² + (b*₁-b*₂)².
According to DIN 53218, Delta E is assigned the following meanings:
0: No colour difference
1: Slight colour difference
2: Small colour difference
3: Medium colour difference
4: Large colour difference
5: Very large colour difference
In industrial colour measurement, colour differences between 0 and 1 often play an important role.