Transcript 2320Lecture13.pptx

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
Autostereograms
Now cross your eyes:
•right-eye line of sight crosses lefteye line of sight in front of image
(crossed convergence)
•each retina is now pointed at the
opposite box
•How many boxes would you see?
crossed convergence
•What would happen to the face?
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
Autostereograms
Crossed convergence shifts right image to the
right of the left image and vice versa:
Left Eye’s Image
Right Eye’s Image
Autostereograms
What would happen if the convergence was
uncrossed?
Autostereograms
Uncrossed convergence shifts right-eye’s image to the
left of the left-eye image and vice versa:
Left Eye
Right Eye
Autostereograms
What would happen if the faces were switched relative
to the boxes?
Autostereograms
• one doesn’t even need two different
images!
Autostereograms
RIGHT EYE
LEFT EYE
Faces fuse
Convergence tells your brain that the plane of the image
is farther away than it really is
Autostereograms
• Uneven spacing between identical
objects in a single picture can appear as
disparity if the angle of convergence is
inappropriate
Autostereograms
• Uneven spacing between identical
objects in a single picture can appear as
disparity if the angle of convergence is
inappropriate
• TRICK: Seeing depth in
autostereograms requires you to
suppress the reflexive coordination
between convergence and
accommodation
Autostereograms
Any repeating objects that have a spacing different from the background will
have either crossed or uncrossed disparity
RIGHT EYE
LEFT EYE
If you uncross convergence, your right eye gets these faces
shifted slightly to left, left eye gets them shifted to right =
CROSSED DISPARITY
What would you see?
Autostereograms
Any repeating objects that have a spacing difference from the background
will have either crossed or uncrossed disparity
RIGHT EYE
LEFT EYE
If you uncross convergence, right eye gets these faces shifted
slightly to right, left eye gets them shifted to left =
UNCROSSED DISPARITY
What would you see?
Autostereograms
• by adjusting the disparity at different parts of
the image (with a computer usually) one can
make shapes that emerge or recede in depth
“Magic Eye” Stereograms
• Usually viewed with uncrossed convergence
• Imagine gazing farther than the surface (let your eyes
“relax”)
• Now try to notice objects or forms in the blurriness
• As you become aware of shapes, try to focus
(accommodate) the plane of the image without
converging your eyes
Autostereograms
Autostereograms
Autostereograms
Wavelength and Color
• Recall that light is electromagnetic radiation
Wavelength and Color
• Recall that light is electromagnetic
radiation
• Light waves have a
frequency/wavelength
Wavelength and Color
• Recall that light is electromagnetic
radiation
• Light waves have a
frequency/wavelength
• Frequency/wavelength is the physical
property that corresponds (loosely) to
the perception called color
Color Vision
Wavelength
and Color
• Different wavelengths correspond
roughly to the “colors” of the spectrum
Color Vision
Wavelength
and Color
• White light is a mixture of wavelengths
– prisms decompose white light into assorted
wavelengths
Color Vision
Wavelength
and Color
• White light is a mixture of wavelengths
– prisms decompose white light into assorted
wavelengths
– likewise, adding all wavelengths together
makes white light
What happens if you mix several different paints together?
Color Vision
Wavelength
and Color
• Objects have different colors because
they reflect some but not all
wavelengths of light
– the surfaces of objects are like filters that
selectively absorb certain wavelengths
Color Vision
Perceiving
Color
• Primary colors
What are the primary colors?
Color Vision
Perceiving
Color
• Primary colors
Red Green Blue
Color Vision
Perceiving
Color
• Primary colors
What makes them primary?
Color Vision
Perceiving
Color
• Primary colors
• Every color (hue) can be created by
blending light of the three primary colors
in differing proportions
Color Vision
Perceiving
Color
• Primary colors
• Every color (hue) can be created by
blending light of the three primary colors
in differing proportions
• Led to prediction that there must be
three (and only three) distinct color
receptor types
Color Vision
Perceiving
Color
Absorption/Cone response
• Four absorption peaks in retina: 3 cone types plus
rods
Color
Theories
ofVision
Color Vision
Wavelength Input
Cone
“Blue”
“Green”
“Red”
Signal to Brain
Blue
Color
Theories
ofVision
Color Vision
Wavelength Input
Cone
Signal to Brain
“Blue”
“Green”
“Red”
Green
Color
Theories
ofVision
Color Vision
Wavelength Input
Cone
Signal to Brain
“Blue”
“Green”
“Red”
Red
Color
Theories
ofVision
Color Vision
Wavelength Input
Cone
Signal to Brain
“Blue”
“Green”
Equal Parts
Red and
Green =
Yellow
“Red”
Color
Theories
ofVision
Color Vision
Wavelength Input
Cone
Signal to Brain
“Blue”
“Green”
Equal Parts
Red and
Green =
Yellow
“Red”
Color
Theories
ofVision
Color Vision
Wavelength Input
Cone
Signal to Brain
“Blue”
“Green”
Equal Parts
Red and
Green =
Yellow
“Red”
Next Time:
• Color Vision
• Read Land Article for Thursday Feb
28th
• Go skiing