Physiological Depth Cues – Convergence. Physiological Depth Cues – Convergence – small angle...
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Transcript of Physiological Depth Cues – Convergence. Physiological Depth Cues – Convergence – small angle...
Physiological Depth Cues
– Convergence
Physiological Depth Cues
– Convergence– small angle of convergence = far away– large angle of convergence = near
– What two sensory systems is the brain integrating?
– What happens to images closer or farther away from fixation point?
Physiological Depth Cues
– Convergence and accommodation are reflexively linked
Under what circumstances might this be a problem?
Motion Depth Cues
– Motion1. Parallax
Motion Depth Cues
– Parallax
Motion Depth Cues
– Parallax– points at different locations
in the visual field move at different speeds depending on their distance from fixation
Motion Depth Cues
– Parallax
QuickTime™ and aGIF decompressor
are needed to see this picture.
More Depth Cues
• Pictorial Depth Cues
• Physiological Depth Cues
• Motion Parallax
• Stereoscopic Depth Cues
Binocular Disparity
• Your eyes have a different image on each retina– hold pen at arms length and fixate the spot
– how many pens do you see?– which pen matches which eye?
Binocular Disparity
• Your eyes have a different image on each retina– now fixate the pen
– how many spots do you see?– which spot matches which eye?
Binocular Disparity
• Binocular disparity is the difference between the two images
Binocular Disparity
• Binocular disparity is the difference between the two images
• Disparity depends on where the object is relative to the fixation point:– objects closer than fixation project images
that “cross”– objects farther than fixation project images
that do not “cross”
Science
• Science is like a set of procedures:
Identify a question
Science
• Science is like a set of procedures:
Identify a question
Make a Hypothesis
Science
• Science is like a set of procedures:
Identify a question
Make a Hypothesis Make a
Prediction
Science
• Science is like a set of procedures:
Identify a question
Make a Hypothesis Make a
Prediction
Test It
Science
• Science is like a set of procedures:
Identify a question
Make a Hypothesis Make a
Prediction
Test ItPrediction holds
Prediction Fails
Example: The horizontal-vertical illusion
Example: The horizontal-vertical illusion
• Question:
Example: The horizontal-vertical illusion
• Question: Why does the vertical line seem longer?
• Hypothesis:
Example: The horizontal-vertical illusion
• Question: Why does the vertical line seem longer?
• Hypothesis: Wundt -> vertical and horizontal eye movements scan the image differently
• Prediction:
Example: The horizontal-vertical illusion
• Question: Why does the vertical line seem longer?
• Hypothesis: Wundt -> vertical and horizontal eye movements scan the image differently
• Prediction: Stabilized image should eliminate the illusion
• Test:
Example: The horizontal-vertical illusion
• Question: Why does the vertical line seem longer?
• Hypothesis: Wundt -> vertical and horizontal eye movements scan the image differently
• Prediction: Stabilized image should eliminate the illusion
• Test: Illusion is still present in afterimage!
Muller - Lyer Illusion
Muller-Lyer Illusion
• What theory does Gregory take up?
Muller-Lyer Illusion
• What theory does Gregory take up?– Thiery / Woodworth : Muller-Lyer figure
“suggests perspective”
Muller-Lyer Illusion
• What theory does Gregory take up?– Thiery / Woodworth : Muller-Lyer figure
“suggests perspective”
– Is there something about the presence of pictorial depth cues in an image that distorts size?
Depth Cues and Size Distortion
The Ponzo Illusion:
Depth Cues and Size Distortion
The Ponzo Illusion:
Depth Cues and Size Distortion
• The illusion of depth in an image seems to distort the perception of size in the image
Pictures are Weird
• What does Gregory find ambiguous about pictures?
QuickTime™ and aH.263 decompressor
are needed to see this picture.
Pictures are Weird
• What does Gregory find paradoxical about pictures?
The Apparatus
• What does he do to remove the paradox so that the Muller-Lyer figure no longer looks flat?
The Apparatus
Removing the Background
• With background removed, Muller-Lyer figure actually looks 3D
• What prediction can you make about how the perceived size and the perceived distance of the center line are related?
• How did Gregory test that?
Removing the Background
• Perceived size and perceived distance are tightly related
Next Time
• Stereo vision
• Read Pinker for next Thursday