Depth Perception Flashcards
A depth cue when viewing a scene that includes objects whose sizes can be compared to each other
Relative size
Large ballon and small ballon on paper, which one is closest
Larger
Why do we think the larger balloon is closest?
- Because we have no reference, we assume the two balloons are the same size
- the object that produces the smaller retinal image size is perceived as farther away
The ______ cue tells us how far away differenceonjects are relative to each other, but it cant, on its own, tell us exactly how far away any of the objects are
Relative size
If we know how big an object really is, our brains can solve the distance-equals-object-size-divided-by-relative-size relationship to determine absolute distances. This this case we are using the ________ depth cue
Familiar depth
This cue is used when viewing objects of known size
Familiar size
When viewing the railroad, we experience a strong sense of depth because we ______ the width of the railroad track is the same through the scene
Assume
The retinal image size of the rail separation in the background, however, is _____ than in the foreground, creating an illusion of depth
Smaller
Why is linear perspective an illusion
Because all aspects of the photograph are physically the same distance from your eyes
Texture gradient
- our brains consciously ignore the bricks because they are part of the background of the scene, and were usually more interested in objects in the foreground
- and unconsciously notices that some bricks are considerably smaller and higher in the VF than others, therefore the bricks form a texture gradient
The distance to any object sitting not he texture can be ________by comparing it to the part of the texture the objects happen to be sitting on
Accurately judged
Can occur when the view of a scene is partially obstructed
Interposition
A form of interposition, _____ acts as a depth cue because unobscured objects in a picture or actual scene may be perceived as closer than those that are obscured, for example, haze
Clarity
What are some examples of things that act as an inter posing element that obscures the view of objects, causing them to appear more distant
Fog, smoke, rain, smog
When light falls on an object, the object casts a shadow. This is interpreted as falling behind the object; consequently, a sense of depth is created
Lighting and shadow
A monocular observer, standing upright, views an object located on the floor at a distance. Despite the absence of pictorial depth cues, the observer is able to judge correctly the objects distance. How is this done?
- The object makes an angle with the horizaon: angular declination below the horizon.
- the visual system apparently uses this angle to determine object distance
A kinetic monocular depth cue that results when a moving observer fixates on object while noticing the relative motion of surrounding objects
Motion parallax
Brain areas that have cells that encode for parallax information and play a role in processing binocular disparity and motion
MT/V5
During ______, the dioptric power of the lens increases, allowing near objects to be focused clearly on the retina
Accommodation
A binocular depth cue that allows the visual system to determine that the ball is distant to the fixated object
Retinal disparity
Light rays emanating from the most distant ball strike the retina nasally to the fovea, ther etinal disparity is said to be _____
Uncrossed
When light rays from the nearest ball strike the retina temporal to the fovea,ther etinal disparity is said to be _______
Crossed
In bino, focusing on an object hits the retina
Nasally
In bino, focusing on the nearest ball strikes the retina
Temporally
Focusing on the middle ball, strikes the retina
On the fovea
The perception of depth production by retinal disparity in a normal binocular vision
Stereopsis
Important contributor to depth perception at near distances
Stereopsis
Why does stereopsis not affect far distances much
Because the threshold for the retinal disparity, which is a specified as an angle at the eye, requires such objects to be separates by great distances
Retinal disparity prioduces stereopsis only if it ______ enough to allow fusion
Small
If the disparity is too larger the images fall on the retina positions that signal grossly different directions, result in
Physiological diplopia
Certain illusions result when pictorial depth cues are used to determine object size
Size illusions
Our visual system compensates for differences in retinal image size by taking into account the relative distance of an object, a phenomenon referred to as
Size constancy
When judgments of distance are erroneous, such as when viewing a flat picture, size constancy may fail, resulting in a
Size illusion
Apparent size of an object with viewing distance
In spite of changes in retinal image size, the apparent size of an object does not normally change with viewing distance
Although a car that us nearby produces a larger retinal image than when it is further away, it is not perceived as
Larger
Size constancy fails because monocular depth cues provide incorrect information regarding relative distance
Corridor illusion
-although the two plaid balls are the same distance from your eyes, the top one is perceived as farther away, this leads to the illusion that the top ball is larger. In fact, the two balls have the same dimensions
When viewed on the horizon, the moon appears larger when viewed at its zenith, even though its angular subtense is the same under conditions
Moon illusion
Considered by some to be a size illusion, because trees, houses, fields, and other inter posing objects cause the moon to be seen as farther away when viewing on the horizon, it appears larger
Moon illusion
Understood by sonsidered the vertical lines to be corners of a room. The line that appears the form an outgoing corner is judged as further away than the line that appears to form an ingoing corner. Because the lines are equal in length, the line that us judged to be farther away is perceived as longer
Muller-lyer illusion
The measurement of a patients stereopsis proves what impritant info
The minimum amount of disparity required to perceive depth is determined. Stereoacuity
The minimum amount of disparity required to perceive depth is determined as the patients ______
Stereoacuity
Can be as small as 3 seconds of arc
Disorders of buinocualr vision
May alter an infants visual experience and retard the development of binocular cortical neurons, resulting in reduction in stereoacuity, consequently, the clinical measurement of stereoacuity proceeds important information regarding a patients visual development and binocular status
Common clinical practice correcting one eye of a presbyopia for distance and the other eye for near, thereby enabling the patient to alternate between the two eyes to see both distant and neat objects clearly
Monovision
Monovision and stereopsis
Can lead to problems with stereopsis because the patients binocularity is impaired
Monovision and diplopia
Usually does not cause diplopia
Why can a monovision patient maintain depth perception
Because many important cues to depth are monocular
A patient with one and eye and depth perception
A patient with one eye manifests excellent depth perception. Althoughstereopsis is an important depth cue for near distances, especially within arms length, it is less important at greater distances
Will monovision correction cause a reduction in stereopsis that interferes with driving safety ?
This is not an easy q to answer because each individual adapts to moon vision at a different rate and to a different extent. Some patients perform well with monovion, while others do not. Although many of the judgements requires in driving are for far distances where stereopsis is less important, other judgments are for relatively near distances
Perceived as strongly when viewed with one eye as when viewed with both eyes.
Monocular depth cues
Major classes of monocular depth cues
Pictorial
Accommodation
Motion parallax
Angular declination
Pictorial depth cues
2D representation, such a photograph or painting
- relative size
- familiar size
- linear perspective
- texture
- interposition
- clarity
- lighting
- shadow
Monocular individuals and depth perception
Manifests surprisingly robust depth perception due largely to these cues
Binocular depth cues
Retinal disparity
Convergence
Depth cues that can be presented in a 2D representation such as a photo or painting
Pictorial depth cues
What are the pictorial depth cues
Relative size Familiar size Linear perspective Texture Interposition Clarity Lighting Shadow
A depth cue that compares the size of objects to each other
Relative size
The object that produces the smaller image size is perceived as being
Farther away
Which of the following depth cues are experienced when viewing a photo
Texture
When viewing a railroad, we experience illusion of depth because of
The retinal image size of the rail separation in the background is smaller than for the foreground
The distance to any object could be determine by which of the following depth cues
Texture gradient
Interposing can occur when the scene is _______ obstructed
Partially
Which of the following depth cues cause the illusion that an object is much more distance than it is
Clarity
Which of the following depth cues are not pictorial depth cues
Motion parallax
When an object is located closer to the observer than the fixated object, the observed disparity is
Crossed
As the viewing distance increases usefulness of stereopsis generally
DECREASES
During monocular ophthalmoscopy, you see a brown spot. When using the iris as a reference, motion parallax shows with motion. The brown spot is likely located on the
Posterior surface of the lens
Which of the following depth cues will not be experienced by a patient with mono vision
Convergence
A monocular individual may use which of the following to determine the distance of an object
Angular declination and motion parallax
A subject fixates a target located 125cm away. While fixating this target, the patient is aware of a circle located at a distance of 175cm. This second circle produces
Uncrossed retinal disparity
Stereopsis may be impaired in
Anismometropia and strabismus
Monoviions contact lenses typically cause stereo-sis to
Become worse
Motion parallax information is encoded in
MT/V5
When viewing a picture, if we experience erroneous judgment of the distance it is _____
Size illusion
The appearance of the moon in the horizon being larger than at the zenith is an example of _______ of objects
Interposition
The outgoing corner in the muller-lyer appears to be _____ than the ongoing corner
Shorter
The test to determine minimum disparity required to perceive depth is
Stereopsis
