Chapter 4-Color and depth perception

Question 1

Color

Answer 1

Secondary quality that can help discriminate objects and have semantic associations

Question 2

Romantic Red

Answer 2

Colors can elicit emotions

Question 3

Wavelength and color

Answer 3

Close correlation between wavelength and color but light waves themselves are colorless
-620-700nm = Red
-590-620nm = Orange
-575-620nm = Yellow
-500-575nm = Green
-450-490nm = Blue
400-450nm = Violet

Question 4

Visible color spectrum

Answer 4

We can distinguish hundreds of colors but tend to perceive colors categorically
-Primary
-Secondary
-Tertiary

Question 5

Additive color mixing

Answer 5

Combining of reflected light waves

Question 6

Subtractive Color Mixing

Answer 6

Mixing physical substances “cancelling” wavelengths
-Pigment combinations absorb more(subtract) wavelengths

Question 7

Principle of Univariance

Answer 7

Infinite set of wavelength and intensity combinations can elicit the same response from a single photoreceptor

Question 8

Three cones

Answer 8

Three cones on the retina differing in their spectral sensitivity
-S = Blue
-M = Green
-L = Red

Question 9

Trichromatic Theory

Answer 9

Under photopic (normal illumination) conditions, all 3 cones are active
-Having three cones allows us to differentiate wavelengths/colors
-Unique pattern of activation across three cones determines what color you perceive

Why three?
Metameric matching experiment shows you need 3 cones to create metamers
-Two is not enough and more than 3 does not help

Question 10

Opponent Color Theory

Answer 10

-After visual info leaves retina it stops in LGN
-LGN has cone (color) opponent cells with center-surround organization
(Cone signals are combined in LGN)
-Theory proposes color perception depends on the output of three color opponent neurons or channels

Chromatic Channels:
-Red/Green
-Yellow/Blue
Achromatic Channels:
-White/Black
-Perception depends on the output of these channels

-Evidence for theory:
-Illegal color combos:
-Illegal color combos are when you combine two opponent colors, you can’t see any original colors in product
-Negative Afterimages

Question 11

Color vision deficiencies

Answer 11

Cone Dichromats (Two functioning cones)
-Deuteranopia (Missing L cones)
-Protanopia (Missing M cones)
-Tritanopia (Missing S cones)

Monochromatism (One or no cones)
-Cone monochromat (One cone)
-Rod monochromat (No cones)

Question 12

Color Constancy

Answer 12

Surfaces tend to be the same color under a wide range of illuminants

Question 13

Color Assimilation

Answer 13

Two different colors ‘Blend’ into each other or ‘average’ each other out
-Each color takes on some of the chromatic qualities of the other

Question 14

Issues with depth perception

Answer 14

-World exists based on Euclidean Geometry but retinal images are Non-Euclidean
(Images are distorted and flipped)

Question 15

Monocular v. Binocular depth cues

Answer 15

Visual cues provide info about depth
-Monocular:
Available when the world is viewed with one eye (both are ok too)

-Binocular:
-Must rely on both eyes

Question 16

Monocular cue: Occlusion

Answer 16

Does not provide exact distance to objects just the relative ordering of objects

Question 17

Monocular cue: Shading

Answer 17

Light comes from above, so shadowed areas suggest depth

Question 18

Monocular cue: Familiar size

Answer 18

Familiar size of an object can aid depth perception, if the object is a known size

Question 19

Monocular: Relative Size

Answer 19

When smaller retinal images of same object are perceived farther away

Question 20

Monocular: Relative height

Answer 20

Relative height is based on an objects height in the visual field
Lower = closer
Higher = farther

Question 21

Monocular: Ariel perspective

Answer 21

Light is scattered all over the place
-The farther light travels and more scattering that occurs, the bluer things appear to be

Question 22

Monocular: Texture Gradient

Answer 22

When we see objects up close we can easily see distance between them

Question 23

Monocular: Linear Perspective

Answer 23

When parallel lines are perceived to be parallel indefinitely

Question 24

Monocular: Motion parallax

Answer 24

Images closer to an observer move faster across the visual field than images farther away

Question 25

Binocular depth perception

Answer 25

Based on binocular disparity created between retinal images -Binocular disparity: -Difference in retinal images between the eyes produced by the same objects in visual field

Question 26

Corresponding v. Non-Corresponding retinal points

Answer 26

Corresponding: -Image is at the same point on each retina E.g, Any image at the fovea Non-corresponding: -Image locations differ between retinas

Question 27

Horopter (Vieth-mueller circle)

Answer 27

-Imaginary plane in the visual field that passes through an object of focus and the retina -Objects on the horopter have corresponding retinal points

Question 28

Crossed v. Uncrossed disparity

Answer 28

Crossed: -Created by objects in front of the horopter -Closer to you Uncrossed: -Created by objects behind the horopter -Farther than you

Question 29

Stereopsis (binocular summation)

Answer 29

-Combining retinal images from the two eyes -Indicates the visual system has overcome the correspondence problem

Question 30

Perceiving Size

Answer 30

-Visual angle is insufficient to perceive distance or size of an object because a visual angle is able to be produced with an infinite # of size/distance combos Size Distance Scaling Function: S = R x D -Perceived size (s) is a product of: -Retinal Image size (R) -Distance (D)

Question 31

Size constancy

Answer 31

Objects of a familiar size are perceived to remain the same size

Question 32

Mueller-Lyer Illusion

Answer 32

Perceived size illusion that may be due to misapplied depth cues -Misapplied size scaling: -Retinal image size is the same in both -But Distance is perceived greater judged greater in #2 Better explained by Conflicting cues -Perception of size is influenced by object AND surround Ex: <------> >-------<

Question 33

Ponzo Illusion

Answer 33

Misinterpretation of size induced by linear perspective

Question 34

Moon Illusion

Answer 34

Moon appears smaller at zenith than on the horizon -Misapplied size scaling? -Conflicting cues(relative size)?