4. 4
Color difference(ΔE) measurements
• Delta CIELAB and CIELCH Assessment of color is more than
a numeric expression. Usually it’s an assessment of the
TOTAL color difference (delta) from a known standard to a
given sample. Commonly CIELAB and CIELCH are used to
compare the colors of two objects
One measure of the difference in colour between two stimuli
or Objects is the Euclidean distance ΔE between the two
points in the three-dimensional space.
ΔE = { (ΔX)2
+ (ΔY)2
+ (ΔZ)2
}1/2
• The term ΔEis derived from the German word for
sensation Empfindung. ΔE therefore literally means
difference in sensation.
5. Color difference Equation index
• CIE 1976 L*, a*, b* (CIELAB) (rectangular
coordinate)
ΔE*ab=[(ΔL*)2
+ (Δa*)2
+(Δb*)]1/2
ΔL=L* sample-L* standard
Δa*=a* sample-a*standard
Δb*=b* sample-b*standard
CIE 1976 L*,C*,H*(CIELAB)(Polar coordinate)
ΔE*ab=[(ΔL*)2
+ (ΔH*)2
+(ΔC*)]1/2
where ΔH* is difference in hue, and
ΔC* is difference in Chroma of sample and standard.
NB ΔH* =Lab Δh* (π/180) is metric hue difference
and Δh* is metric hue angle diffrences.
