Problem 6 – Coren & Goldstein
PERCEIVING DEPTH
Types of depth perception:
- Absolute distance: perception of the actual distance of an object
o involves a process called egocentric localization: meaning we have a good sense of
where our bodies are positioned
- Perception of relative distance: this judgement requires object-relative localizations
which are estimates of the distances between objects in the environment
How do we get a 3- dimensional perception from a flat 2-D image on the retina?
- Cue approach to depth perception: identifies information in the retinal image that is
correlated with depth in scene
- We learn the connection between these cues and depth through our previous experiences
in the environment
- After learning the association between cues and depth becomes automatic
3 groups for cues:
- Oculomotor: cues based on our ability to sense the position of our eyes and the tension in
our eye muscles
- Monocular: cues that work with one eye
- Binocular: cues that depend on 2 eyes
Oculomotor Cues: created by:
- Convergence: the inward movement of the eyes that occurs when we look at nearby
objects
- Divergence: when an object is further away the eyes move away from each other in an
outward rotation
- accommodation: the change in the shape of lens that occurs when we focus on objects at
various distances
o relaxed accommodation: the lens is flattened for distant objects to be seen
o strongly curved lens: needed to see closer objects
Monocular cues: work only with one eye
- includes 1) “accommodation” and 2) “pictorial cues”: depth information that can be
depicted in a two-dimensional picture, & 3) “movement-based cues”: based on depth
information created by movement
2) Pictorial cues:
- Occlusion/Interposition: when an object is in front of another object, the covered one
should be at greater distance
- Relative height/height in a plane: when objects are closer to the horizon, they seem more
distant
o When objects are below the horizon with bases higher in the field of view seem
more distant
o When the objects are above the horizon, like clouds, with bases lower in the field of
view seem more distant
, - Relative size: when two objects are of equal size, the one that is further will take up less of
your field of view
- Perspective convergence/Linear perspective: When parallel lines extend out from an
observer, they are seen as converging – becoming closer – as distance increases
- Familiar size: we judge a distance based on our prior knowledge of sizes of objects
- Atmospheric/Aerial perspective: occurs when more distant objects appear less sharp and
often have a slight blue tint
o the further away an object is, the more air and particles we have to look through
making objects less sharp and bluer than close objects
- Texture gradient: elements that are equally spaced in a scene appear to be more closely
packed as distance increases
- Shadows: can provide information regarding the locations of objects
o Surfaces facing the light will be relatively bright, and surfaces facing away from the
light source will be in shadow
o Attached shadow: help us indicate the intrinsic shape of an object
o Cast shadow: indicate the relative distance of an object from another object or
surface
3) Motion-produced cues:
- Motion parallax: when we move, nearby objects appear to glide rapidly past us, but more
distant objects appear to move more slowly
o Can also be generated by swinging your head back and forth
o Kinetic depth effect: motion cues can give us information about the relative depth
of parts of an object
- Deletion and accretion: as we move sideways, some things become covered others
become uncovered – related to both motion parallax and overlap
Binocular depth information
Binocular disparity: difference in the images in the left and right eyes
- Corresponding retinal points: the places on each retina that
would overlap if one retina could be put on top of the other
- Horopter: imaginary surface that passes through the point of
fixation and indicates the location of objects that fall on the
corresponding points on 2 retinas
- Susan, Frieda and Harry fall on corresponding points, but
Carole falls on noncorresponding points (they would not
overlap if you put 2 eyes on top of each other)
- Angle of disparity: the difference between where Carole’s
image falls on the right eye and the corresponding point
- Absolute disparity: absolute angle of disparity – 26 degrees
o Provides information about the distances of objects
o Greater disparity is associated with greater distance
from the horopter
o It changes every time the observes changes where
s/he is looking
o Relative disparity: the difference between 2 objects’
absolute disparities – disparity information that
remains the same no matter where the observer looks
PERCEIVING DEPTH
Types of depth perception:
- Absolute distance: perception of the actual distance of an object
o involves a process called egocentric localization: meaning we have a good sense of
where our bodies are positioned
- Perception of relative distance: this judgement requires object-relative localizations
which are estimates of the distances between objects in the environment
How do we get a 3- dimensional perception from a flat 2-D image on the retina?
- Cue approach to depth perception: identifies information in the retinal image that is
correlated with depth in scene
- We learn the connection between these cues and depth through our previous experiences
in the environment
- After learning the association between cues and depth becomes automatic
3 groups for cues:
- Oculomotor: cues based on our ability to sense the position of our eyes and the tension in
our eye muscles
- Monocular: cues that work with one eye
- Binocular: cues that depend on 2 eyes
Oculomotor Cues: created by:
- Convergence: the inward movement of the eyes that occurs when we look at nearby
objects
- Divergence: when an object is further away the eyes move away from each other in an
outward rotation
- accommodation: the change in the shape of lens that occurs when we focus on objects at
various distances
o relaxed accommodation: the lens is flattened for distant objects to be seen
o strongly curved lens: needed to see closer objects
Monocular cues: work only with one eye
- includes 1) “accommodation” and 2) “pictorial cues”: depth information that can be
depicted in a two-dimensional picture, & 3) “movement-based cues”: based on depth
information created by movement
2) Pictorial cues:
- Occlusion/Interposition: when an object is in front of another object, the covered one
should be at greater distance
- Relative height/height in a plane: when objects are closer to the horizon, they seem more
distant
o When objects are below the horizon with bases higher in the field of view seem
more distant
o When the objects are above the horizon, like clouds, with bases lower in the field of
view seem more distant
, - Relative size: when two objects are of equal size, the one that is further will take up less of
your field of view
- Perspective convergence/Linear perspective: When parallel lines extend out from an
observer, they are seen as converging – becoming closer – as distance increases
- Familiar size: we judge a distance based on our prior knowledge of sizes of objects
- Atmospheric/Aerial perspective: occurs when more distant objects appear less sharp and
often have a slight blue tint
o the further away an object is, the more air and particles we have to look through
making objects less sharp and bluer than close objects
- Texture gradient: elements that are equally spaced in a scene appear to be more closely
packed as distance increases
- Shadows: can provide information regarding the locations of objects
o Surfaces facing the light will be relatively bright, and surfaces facing away from the
light source will be in shadow
o Attached shadow: help us indicate the intrinsic shape of an object
o Cast shadow: indicate the relative distance of an object from another object or
surface
3) Motion-produced cues:
- Motion parallax: when we move, nearby objects appear to glide rapidly past us, but more
distant objects appear to move more slowly
o Can also be generated by swinging your head back and forth
o Kinetic depth effect: motion cues can give us information about the relative depth
of parts of an object
- Deletion and accretion: as we move sideways, some things become covered others
become uncovered – related to both motion parallax and overlap
Binocular depth information
Binocular disparity: difference in the images in the left and right eyes
- Corresponding retinal points: the places on each retina that
would overlap if one retina could be put on top of the other
- Horopter: imaginary surface that passes through the point of
fixation and indicates the location of objects that fall on the
corresponding points on 2 retinas
- Susan, Frieda and Harry fall on corresponding points, but
Carole falls on noncorresponding points (they would not
overlap if you put 2 eyes on top of each other)
- Angle of disparity: the difference between where Carole’s
image falls on the right eye and the corresponding point
- Absolute disparity: absolute angle of disparity – 26 degrees
o Provides information about the distances of objects
o Greater disparity is associated with greater distance
from the horopter
o It changes every time the observes changes where
s/he is looking
o Relative disparity: the difference between 2 objects’
absolute disparities – disparity information that
remains the same no matter where the observer looks
