Lecture 5 & 6

Question 1

What does colour enhance?

Answer 1

Perceptual organisation
Top down control
Automatic bottom up processing

Question 2

Colours for wavelengths:
short/medium 
medium 
medium/long
long

Answer 2

blue
green
yellow
red

Question 3

What are the colours of solid objects?

Answer 3

Reflected wavelengths
Chromatic colours are the result of selective reflection (some reflected others absorbed)
Achromatic colours are the result of equal reflection

Question 4

Colours of transparent objects

Answer 4

Chromatic colours are the result of selective transmission (some colours absorbed and some transmitted)

Question 5

3 Colour dimensions in terms of Hue, Saturation and brightness

Answer 5

Hue: colour wheel
Saturation: amount of white added to the colour
Brightness: The amount of light reflected/intensity of the light

Question 6

Mixing light

Answer 6

Additive colour mixture, combination of wavelengths

Question 7

Mixing pigments

Answer 7

Subtractive colour mixture. Pigments will absorb the same wavelengths they absorb when they are alone. Only wavelengths reflected that are common in both pigments

Question 8

Theories of colour

Answer 8

Trichromatic theory

Opponent process theory

Question 9

Trichromatic theory

Answer 9

Young & Hemlhots

Colour matching experiments.

Question 10

Results of trichromatic theory

Answer 10

Any colour can be matched by correctly adjusting 3 different wavelengths, not 2. Full colour vision is based on the ability to combine 3 wavelengths.

Question 11

Physiological evidence of trichromatic theory

Answer 11

S = short wavelengths
M = medium wavelengths
L = long wavelengths

Question 12

Monochromatism

Answer 12

No functioning cones so only perceive shades of brightness

Question 13

Dichromatism

Answer 13

Protanopia (no L cones)
Deuteranopia (no M cones)
Tritanopia (no S cones)

Question 14

Tetrachromacy

Answer 14

Some animals have 4 types of cones so have 4 dimensional colour space

Question 15

Opponent process theory

Answer 15

Hering 
complementary afterimages 
Adapting " generates " afterimages
blue => yellow
green => red
black => white

Question 16

What opponent channels respond in opposite ways to different wavelengths?

Answer 16

Black/white
Red/green
Blue/yellow
Resulting in these as blindness

Question 17

Oculomotor cues

Answer 17

Cues that include accommodation and convergence. Body related cues

Question 18

What are stimulus related cues?

Answer 18

monocular cues (with one eye) 
binocular cue (both eyes)

Question 19

What are involved in monocular cues?

Answer 19

Occlusion, relative height, relative size, perspective convergence, familiar size, atmospheric pressure, texture gradients, shadows

Question 20

Occlusion (monocular cues)

Answer 20

occluded objects (partially hidden) appear further away

Question 21

Relative height (monocular cue)

Answer 21

Objects higher in the visual field are further away than objects in the lower field.

Question 22

Relative size (monocular cues)

Answer 22

when objects are equal in size the one that is further away takes up less of the visual field

Question 23

Familiar size (monocular cue)

Answer 23

knowledge about physical size of an object

Question 24

Perspective convergence

Answer 24

converging parts of an object are further away

Question 25

Atmospheric pressure

Answer 25

Objects that are further away are less sharp and have a blue tint. Particles in the atmosphere scatter light and soften colours.

Question 26

Texture gradients

Answer 26

Denser textures indicate objects are further away

Question 27

Motion based cues

Answer 27

motion parallax (near objects move quicky and far away objects move slowly), deletion and accretion

Question 28

Deletion and accretion

Answer 28

an object being covered and uncovered is further away. If you look at something in the distance and you move the object also appears to move

Question 29

Depth cues

Answer 29

Body related Stimulus related Binocular cues

Question 30

Binocular cues

Answer 30

Retinal disparity and stereoscopic vision

Question 31

Retinal disparity

Answer 31

The retinal images in the left and right eyes are a few cm apart

Question 32

Horopter

Answer 32

Imaginary plane through the fixation point connecting all objects of which retinal images fall on corresponding retinal points

Question 33

Stereopsis

Answer 33

The ability to use retinal disparity as a cue to perceive depth. The larger the disparity the further away the object is from fixation.

Question 34

Ponzo illusion

Answer 34

Two objects that are the same size appear different sizes in images due to their relative location. The size of an object is determined by its degree of visual angle.

Question 35

Calculating size constancy

Answer 35

S = K ( R X D) S perceived size R size of the retinal image D perceived distance