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Study Guide

[PSYB57H3] - Final Exam Guide - Comprehensive Notes fot the exam (214 pages long!)


Department
Psychology
Course Code
PSYB57H3
Professor
George Cree
Study Guide
Final

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UTSC
PSYB57H3
FINAL EXAM
STUDY GUIDE

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Lecture 5 and Chapter 5
Basic Principles of Colour Perception
colours are in our mind
colour: not a physical property but rather a psychophysical property
o most of the light we see is reflected
o typical light sources: sun, light bulb; emit a broad spectrum of wavelengths
o 400-700nm is the visible spectrum
One colour filters will take out other colours
Cones are like filters
Sone filter out light of small wavelength and or large filter light
One filter is not enough to see all the colours in the image
Problem of Univariance: an infinite set of different wavelength-intensity combinations can elicit
exactly the same response from a single type of photoreceptor
o One type of photoreceptors cannot make colour discrimination based on wavelength
Thee ae’t e/gee/lue oes
Trichromacy
Scotopic: referring to dim light levels at or below the level of bright moonlight
o Rods are sensitive to scotopic light levels
o All rods contain same type of photopigment molecule: rhodopsin
o All rods have same intensity to wavelength making it impossible to discriminate light
Photopic: light intensities that are bright enough to stimulate the cone receptors and bright
enough to saturate the rod receptors.
Newton: prisms break up sunlight into spectral components ( and put it back again) (colour not a
physical property, must be a form of sensation
Young- Helmholtz (-Maxwell) theory: theory of trichromatic colour vision. Colour vision is based
on 3 photoreceptors sensitive to particular ranges of wavelength
Maell’s olou athig tehiue
We only need 3 types of colour to make other colour
Types of cones:
o S-cone: cones that are preferentially sensitive to short wavelengths, 440 nm (blue
cones)
o M-cones: cones that are preferentially sensitive to middle wavelength, 535nm (green
cones)
o L-cones: cones that are preferentially sensitive to long wavelengths, 565nm (red cones)
with 3 cone types we can tell the difference between lights of different wavelengths
Metamers: any pair of stimuli that are perceived as identical in spite of physical differences. In
terms of light: different mixtures of wavelength that look identical
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Additive colour mixture: a mixture of lights. If lights A and light s B are both reflected from a
surface to the eye, in the perception of colour, the effects of those two lights add together
Subtractive colour mixture: a mixture of pigments. If pigment A and pigment B mix, some of the
light shining on the surface will be subtracted by A, and some B. Only the reminder contributes
to the perception of colour.
Colour pace is 3D because we have 3 cones
o Hue: chromatic aspect of colour
o Saturation: chromatic strength of a hue, faded or not
o Brightness: distance from black in colour space
Non-spetal hues: hues that do’t eist as pue fos of light but only as mixtures of different
wavelengths
Heis’s idea aout soe olous eig illegal
o Opponent colour theory: the theory that perception of colour is based on the output of
the three mechanism, each of them on an opponency between two colours; red-green,
blue-yellow, and black-white
o Achromatic system is the mixture of all cones which makes black and or white
o Chromatic system is the mixture of certain colours such as blue and yellow or red and
green
o Psychophysical support for the opponent colour theory
Afterimage: a visual image seen after the stimulus has been removed
First you view the adapting stimulus, than look at the negative
afterimage
LGN has colour opponent cells: neurons whose output is based on a difference
between sets of cones
Colour system in V1: blobs
Colour system in V2: thin stripes
Zeki 1993: human V4 = colour area
Achromatopsia: an inability to perceive colours that is due to damage to the
central nervous system
Metameres is a trick to see whether people can see pure colour light o if it’s a itue
Ishihara test: is the bubbles that makeup a number to one has to tell whether they can see it or
not, colour blindness test
Two types of colour blind people
o Cone monochromat: only have one cone type: truly colour blind, only see black and
hite, a’t see duig dakess
o Rod monochromat: no cones of any type: truly colour-blind, badly visually impaired in
bright light, normal during night but need sungalsses in the morning
Three types of colour-anomalous people:
o Deuternope: no m cones, only sees blue and yellow
o Protanope: no L cones
o Trianope: no s cones, cant see blue
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