7. metamerism

METAMERISM

CHAPTER-7

Granch Berhe

Metamersim• The word Metamerism is used to describe the phenomenon

observed when two surfaces are similar in colour under one set of viewing conditions, but different under another.

• There are three manifestations of Metamerism Illuminant Metamerism Observer Metamerism Geometric Metamerism• Another Metamerism that may be combination of observer

and geometric Metamerism, depends on the size of the sample and distance from which they are viewed.

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Visual color assessment

• Color of a sample=Color of the standardOr

Color sensation produced by a sample=Color sensation produced by a standard.

(H, S, V)sample= (H,S,V) standard

Instrumental color assessment

• 1) Color of standard=Color of sample i.e., Tristimuls values of standard equals

tristimulus values of Sample(X,Y,Z)standard = (X,Y,Z)sample2)Spectral reflectance =Spectral reflectance curve of standard curve of sample3) ΔE = { (ΔX)2+ (ΔY)2+ (ΔZ)2}1/2 Should be zero or very small

number less or equals 1.