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Color vision metamers and theories of color perception in making colors, metamers and opponent process theory
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This yellow can be made from a mixture of red and green lights ...
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Different spectra, Same perceived colour
If you had only one cone type then the output produced by a given wavelength (eg 520nm) can be reproduced exactly by a different wavelength (600nm). The same type of behaviour ensures that many different spectra can induce the same outputs in the three cone types. This is the principle of univariance : a cone’s output indicates how much light it absorbed, not the wavelength of that light.
Wavelength λ L-cone response To test light Test light M-cone response To test light Metameric matching for two cone types
10 Wavelength λ L-cone response To test light Test light M-cone response To test light Green torch L-cone response To green torch M-cone response To green torch ‘Difference in M-cone output Difference in L-cone output Metameric matching for two cone types
11 Wavelength λ L-cone response To test light Test light M-cone response To test light Red torch Green torch L-cone response To green torch M-cone response To green torch ‘Missing’ M-cone output ‘Missing’ L-cone output Metameric matching for two cone types
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cones -10mV -20mV -30mV Perceived^ colour2= perceived colour Luminance spectrum2=/=spectrum reflected from white surface
Torch wavelengths Cone triplet outputs
LIGHT INPUT OUTPUT
PROCESS EXPERIENCE OF COLOUR PERCEPTION In order to understand colour perception, we must establish what takes place here. A first stage in doing this is to consider the facts about the psychological experience of colour perception. This was what the original theories of colour perception were based on.
Strengths of Trichromatic Theory
Doesn’t fully explain colour blindness: In reality, colour loss in colour blindness occurs in pairs: inability to discriminate pairs red-green or yellow-blue. Colours are never lost in isolation and pairings other than those above are never found. Weaknesses of Trichromatic Theory