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Perception: Maastricht University > Task 3: Colour > Flashcards

Task 3: Colour Flashcards

1
Q

“Pure/unique” colors

A

red, yellow, green, blue - all colors can be described with these

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2
Q

Desaturation

A

changing color by making light brighter by adding white e.g. red + white = pink

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3
Q

Name the 3 Types of Cone Pigments

A

S - 419 max - blue
M - 531 max - green
L - 558 max - red

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4
Q

Chromatic colors/hues

A

(e.g. blue, green, red) occur when some wavelengths are reflected more than others through a process called selective reflection

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5
Q

Selective reflection

A

objects selectively reflect some wavelength (opaque objects) -> chromatic colours more

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6
Q

Selective transmission

A

only some wavelengths pass through the object/substance (transparent objects) e.g. cranberry juice

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7
Q

Transmission curves

A

plots of the percentage of light transmitted vs wavelength

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8
Q

Additive color mixing

A

mixing lights involves adding up the wavelengths of each light in the mixture

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9
Q

Subtractive color mixture

A

mixing paints causes fewer wavelengths to be reflected because each paint subtracts wavelengths from mixture

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10
Q

How is black created in relation to subtractive colour mixing

A

when reflected wavelengths of 2 colors differ, however is rare

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11
Q

Trichromatic theory of colour vision

A

colour vision depends on the activity of 3 different receptor mechanisms, based on the psychophysical procedure called colour matching

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12
Q

Colour matching experiements

A

observers adjusted the amounts of 3 different wavelengths of light mixed together in a “comparison field” until the colour matched the colour of a single wavelength in a “test field”

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13
Q

Young-Helmholtz Theory of Color Vision

A

colour vision depends on 3 receptor mechanisms, each with different spectral sensitivities

  • > Light of a particular wavelength stimulates each receptor mechanism to different degrees and the pattern of activity in the 3 mechanisms results in colour perception
  • > Therefore, each wavelength is represented in the NS by its own pattern of activity in the 3 receptor mechanisms
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14
Q

How is white formed by receptors?

A

equal signalling of all 3 receptors

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15
Q

How are cones responsible for 3 different absorption spectra?

A

the long opsin part of the visual pigments differ

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16
Q

Metamerism

A

when 2 physically different stimuli are perceptually identical e.g. lights in the trichromatic experiment being physically different but perceptually identical

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17
Q

Metamers

A

2 identical fields (lights) being perceptually identical but not physically the same, this is due to them resulting in the same pattern of response in 3 cone receptors (2 lights are physically different but when combined look the same)

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18
Q

Isomerization

A

visual pigment isomerizes (retinal changes shape) when the molecule absorbs one photon of light, this activates the molecule and triggers the process that activates the visual receptor to see light

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19
Q

Color deficiency

A

partial loss of colour perception, usually due to problems with retinal receptors present at birth

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20
Q

How can color deficiency be determined?

A

o Colour tests e.g. Ishihara plate
o Using the colour-matching procedure (to determine the minimum number of wavelengths needed to match any other wavelength in the spectrum)

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21
Q

Unilateral dichromat

A

trichromatic vision in one eye, dichromatic vision in the other (can determine for use what a dichromat sees)

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22
Q

Monochromat

a) how many pigments
b) describe wavelengths
c) visual acuity level
d) colors seen

A

a) 1 pigment
b) can match any wavelength in the spectrum by adjusting the intensity of any other wavelength therefore needs only one wavelength to match any colour in the spectrum
c) poor, rod system overloaded in strong illumination, sensitive to bright lights
d) white, grey, black

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23
Q

Dichromat

a) how many pigments
b) describe wavelengths
c) name 3 types

A

a) 2
b) only needs 2 wavelengths to match all other wavelengths in the spectrum
c) protanopia, deuteranopia, tritanopia

24
Q

Protanopia

A

is missing the long-wavelength pigment

25
Q

Deuteranopia

A

is missing the medium-wavelength pigment

26
Q

Tritanopia

A

is missing the short-wavelength pigment

27
Q

How are protanopia and deutranopia inherited

A

through X gene on chromosome, females can carry it and not be colour blind but a carrier (XY)

28
Q

Anomalous Trichromat

A

Needs 3 wavelengths to match any wavelengths however mix these in different proportions therefore not good as discriminating

29
Q

Opponent-process theory of color vision

A

proposed based on behavioural observations (contrasting trichromatic theory based on psychophysical experiments), based onresults of phenomenological observations, in which stimuli were presented and observers described their perception

30
Q

Simultaneous color contrast

A

one colour can change how we perceive the tone and hue of another when 2 are placed side by side

31
Q

3 mechanisms of opponent-process theory of color vision

A

o Black (-) and white (+) mechanism

  • > Responds positively to white light
  • > Responds negatively to the absence of light

o Red (+) and green (-) mechanism

  • > Responds positively to red
  • > Responds negatively to green

o Blue (-) and yellow (+) mechanism

  • > Responds positively to yellow
  • > Responds negatively to blue

o Physiological research showed that these colours do cause physiologically opposite responses

32
Q

Opponent neurons

A

in the retina and LGN, respond with an excitatory response to light from one part of the spectrum and with an inhibitory response to light from another part

33
Q

Areas for processing…

a) face
b) body
c) place

A

a) fusiform face area
b) extrastriate body area
c) parahippocampal place area

34
Q

Cerebral achromatopia

A

: a condition caused by brain damage, cannot see colour (other effects include prosopagnosia)

35
Q

Is there a particular region for color detecting in the brain

A

colour perception results from activity in many different visual areas that respond not only to colour but to other qualities e.g. form

36
Q

Color constancy

A

we perceive colours of objects as being relatively constant even under changing illumination (think- green jumper) -> brain corrects

37
Q

Chromatic adaptation

A

prolonged exposure to chromatic colour, can change colour perception

38
Q

Memory colour

A

knowing the usual colours of objects in the environment -> expectancy effects

39
Q

Achromatic colors

A

grey, white, black

40
Q

Lightness

A

shade of achromatic colour

41
Q

Lightness constancy

A

we see whites, greys, blacks as staying about the same shade under different illuminations

42
Q

Ratio principle

A

as long as this ratio remains the same the perceived lightness will remain the same

43
Q

Ratio of ratio principle

A

Reflectance of the object : Reflectance of surrounding objects

44
Q

Reflectance edge

A

an edge where the reflectance of 2 surfaces change

45
Q

Illumination edge

A

edge where lighting changes

46
Q

3 steps of colour perception

A
  1. detection
  2. discrimination
  3. appearance (despite changing conditions i.e. constancy)
47
Q

Electromagnetic energy is produced by ___ ___ and radiated as ___

A

electric charges, waves

48
Q

Wavelength

A

distance between peaks of electromagnetic waves

49
Q

Reflectance curve

A

plots amount of light reflected vs wavelength

50
Q

How are achromatic colours produced?

A

light is reflected equally across spectrum (white higher percentage of light vs black)

51
Q

Hue cancellation experiment

A

aims at seeing how much of opponent colour needs to be added in order to cancel all perception of other colour

52
Q

Double-opponent cell

A

visual cortex, one region is excited by one cone type, combination of cones or color and inhibited by opponent cones or colour

53
Q

Why does colour constancy occur? x3

A

1 chromatic adaptation
2 effect of surroundings
3 memory colour

54
Q

Amount of light reaching eye from objects depends on x2

A

1 illumination

2 reflectance from object

55
Q

Why does light constancy occur? x2

A

1 ratio principle

2 perception under uneven illumination

56
Q

How does visual system distinguish between 2 edges? x 3

A

Based on
1 shape of the shadow
2 penumbra
3 orientation of surface

Perception: Maastricht University (8 decks)

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