PSYCH 2220Perception

Lecture 8Seeing in colour

Isaac NewtonSpectrumColour mixing (additive, subtractive)MetamersTrichromacy (Young and Helmholtz)

Figure 9.7 Color mixing with paint. Mixing blue paint and yellow paint creates a paint that appears green. This is subtractive color mixture.

Figure 9.9 Absorption spectra of the three cone pigments. From Dartnall, H. J. A., Bowmaker, J. K. and Mollon, J. D. (1983). Human visual pigments: Microspectrophotometric results from the eyes of seven persons. Proceedings of the Royal Society of London B, 220, 115-130.

Short wavelength cones

Medium and long wavelength cones

rods

MonochromatDichromat (all mammals except primates)Trichromat (primates)

COLOUR VISION DEFICIENCIES

ISHIHARA PLATES

x x

Trichromacy vs opponency

Can explain colour matching

Can explain adaptation

Young& Helmholtz

Hering

OPPONENCY THEORY

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RED GREENBLUE

RED-GREENSYSTEM

BLUE-YELLOWSYSTEM

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Colour opponencyis found at the level of RETINAL GANGLION

CELLS

magnocellular

parvocellular

On centre off centre

CONCLUSION

Both trichromacy and colour opponency are correct

P-pathway essential (parvocellular)Lesions in inferotemporal can cause achromatopsia

LEFTEYE

RIGHTEYE

RIGHTEYE

LEFTEYE

OrientationpinwheelsColour

blobs

Organization of a hypercolumn.

Colour blobs

Motion vs still Colour vs grey

SIMULTANEOUS COLOUR CONTRAST

COLOUR CONSTANCY

DIFFERENT SOURCES OF ILLUMINATION HAVE DIFFERENT SPECTRAL CONTENT. But colours look (relatively) the same.

http://www.youtube.com/watch?v=TVUrHf2kcUM