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Extra Credit for Participating in Experiments

Extra Credit for Participating in Experiments. Go to www.tatalab.ca to sign up We are recruiting for a variety of experiments including basic perception and ADHD. ADHD Research Project.

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Extra Credit for Participating in Experiments

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  1. Extra Credit for Participating in Experiments Go to www.tatalab.ca to sign up We are recruiting for a variety of experiments including basic perception and ADHD

  2. ADHD Research Project We are specifically recruiting individuals who have been diagnosed with ADHD and are currently taking medication Contact Karla at karla.ponjavic@uleth.ca for more information or to sign up

  3. Upcoming • Read Gregory Article for Feb 23 • Read Pinker Article for help with stereo vision and stereo grams • Read Land Article for March 2

  4. Depth Cues • Pictorial Depth Cues: aspects of 2D images that imply depth • Physiological Depth Cues: Proprioception in ocular muscles indicates accommodation and convergence • Motion Depth Cues: foreground and background move in opposite directions • Stereoscopic Depth Cues: disparity between two retinal images indicates distance

  5. Pictorial Depth Cues • Retinal image size • far objects smaller than near objects

  6. Pictorial Depth Cues • Retinal image size • problem: big far things same as close small things • “solved” by size constancy: Perceived size is adjusted according to perceived distance (based on other cues) • forms the basis for several visual illusions

  7. Pictorial Depth Cues • Retinal image size

  8. Pictorial Depth Cues • Retinal image size

  9. Pictorial Depth Cues • Linear perspective

  10. Pictorial Depth Cues • Texture gradient

  11. Pictorial Depth Cues • Height in the plane

  12. More Depth Cues • Pictorial Depth Cues • Physiological Depth Cues • Motion Parallax • Stereoscopic Depth Cues

  13. Physiological Depth Cues • Two Physiological Depth Cues • accommodation • convergence

  14. Physiological Depth Cues • Accommodation

  15. Physiological Depth Cues • Convergence

  16. 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?

  17. Physiological Depth Cues • Convergence and accommodation are reflexively linked Under what circumstances might this be a problem?

  18. Motion Depth Cues • Motion • Parallax

  19. Motion Depth Cues • Parallax

  20. Motion Depth Cues • Parallax • points at different locations in the visual field move at different speeds depending on their distance from fixation

  21. Motion Depth Cues • Parallax

  22. Seeing in Stereo Seeing in Stereo

  23. Seeing in Stereo It’s very hard to read words if there are multiple images on your retina It’s very hard to read words if there are multiple images on your retina

  24. Seeing in Stereo It’s very hard to read words if there are multiple images on your retina It’s very hard to read words if there are multiple images on your retina But how many images are there on your retinae?

  25. 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?

  26. 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?

  27. Binocular Disparity • Binocular disparity is the difference between the two images

  28. 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”

  29. Binocular Disparity • Corresponding retinal points

  30. Binocular Disparity • Corresponding retinal points

  31. Binocular Disparity • Corresponding retinal points

  32. Binocular Disparity • Corresponding retinal points

  33. Binocular Disparity • Points in space that have corresponding retinal points define a plane called the horopter The Horopter

  34. Binocular Disparity • Points not on the horopter will be disparate on the retina (they project images onto non-corresponding points)

  35. Binocular Disparity • Points not on the horopter will be disparate on the retina (they project images onto non-corresponding points) • The nature of the disparity depends on where they are relative to the horopter

  36. Binocular Disparity • points nearer than horopter have crossed disparity • points farther than horopter have uncrossed disparity The Horopter

  37. Binocular Disparity • Why don’t we see double vision?

  38. Binocular Disparity • Why don’t we see double vision? • Images with a small enough disparity are fused into a single image

  39. Now on to Magic Eye Stereograms

  40. Stereograms Divider Left Eye Right Eye • Right eye sees face to the left; left eye sees face to the right therefore: • faces present crossed disparity to the brain • Face appears in front of square

  41. Autostereograms • Optically separate images aren’t needed

  42. Autostereograms • Optically separate images aren’t needed • WARNING! Tricky stuff coming in the next slides

  43. Autostereograms • Optically separate images aren’t needed • WARNING! Tricky stuff coming in the next slides • Keep the definitions of convergence and disparity separate.

  44. Autostereograms What would happen if you remove the divider of a stereoscope? • Convergence is on a point at the same distance as the images • Boxes and faces are on the horopter • How many boxes would you see? boxes and faces are on the horopter

  45. Autostereograms Now cross your eyes: • right-eye line of sight crosses left-eye line of sight in front of image (crossed convergence) • each retina is now pointed at the opposite box • How many boxes would you see? • What would happen to the face? crossed convergence

  46. Autostereograms • There would be three boxes • middle box: right eye sees face shifted to right; left eye sees face shifted to left therefore: • uncrossed disparity • Face in the middle box appears behind square crossed convergence

  47. Autostereograms • What would happen if you moved the faces within the box? • What would happen if you viewed this with uncrossed convergence?

  48. Autostereograms Crossed convergence shifts right image to the right of the left image and vice versa: Left Eye’s Image Right Eye’s Image

  49. Autostereograms What would happen if the convergence was uncrossed?

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