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6. colour difference measurement

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colour difference measurement

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6. colour difference measurement

  1. 1. COLOUR DIFFERENCE MEASUREMENT Granch Berhe
  2. 2. C*=Chroma H*= Hue
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  4. 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. 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.
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