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Autostereograms
•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
What would happen if you remove the divider of a stereoscope?
Autostereograms
•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
Now cross your eyes:
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
Left Eye’s ImageRight Eye’s Image
Crossed convergence shifts right image to the right of the left image and vice versa:
Autostereograms
What would happen if the convergence was uncrossed?
Autostereograms
Left EyeRight Eye
Uncrossed convergence shifts right-eye’s image to the left of the left-eye image and vice versa:
Autostereograms
What would happen if the faces were switched relative to the boxes?
Autostereograms
• one doesn’t even need two different images!
RIGHT EYE LEFT EYE
Convergence tells your brain that the plane of the image is farther away than it really is
Autostereograms
Faces fuse
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
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
AutostereogramsAny repeating objects that have a spacing different from the background will have either crossed or uncrossed disparity
What would you see?
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
AutostereogramsAny repeating objects that have a spacing difference from the background will have either crossed or 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
• Different wavelengths correspond roughly to the “colors” of the spectrum
Wavelength and Color
Color Vision
• White light is a mixture of wavelengths– prisms decompose white light into assorted
wavelengths
Wavelength and Color
Color Vision
• 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?
Wavelength and Color
Color Vision
• 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
Wavelength and Color
Color Vision
• Primary colors
Perceiving Color
What are the primary colors?
Color Vision
• Primary colors
Perceiving Color
Red Green Blue
Color Vision
• Primary colors
Perceiving Color
What makes them primary?
Color Vision
• Primary colors
• Every color (hue) can be created by blending light of the three primary colors in differing proportions
Perceiving Color
Color Vision
• 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
Perceiving Color
Color VisionPerceiving Color• Four absorption peaks in retina: 3 cone types plus
rods
Abs
orpt
ion/
Con
e re
spon
se
Color VisionTheories of Color Vision
“Blue”
“Green”
“Red”
Blue
Wavelength Input Cone Signal to Brain
Color VisionTheories of Color Vision
“Blue”
“Green”
“Red”
Green
Wavelength Input Cone Signal to Brain
Color VisionTheories of Color Vision
“Blue”
“Green”
“Red” Red
Wavelength Input Cone Signal to Brain
Color VisionTheories of Color Vision
“Blue”
“Green”
“Red”
Yellow
Equal Parts Red and Green =
Wavelength Input Cone Signal to Brain
Color VisionTheories of Color Vision
“Blue”
“Green”
“Red”
Yellow
Equal Parts Red and Green =
Wavelength Input Cone Signal to Brain
Color VisionTheories of Color Vision
“Blue”
“Green”
“Red”
Yellow
Equal Parts Red and Green =
Wavelength Input Cone Signal to Brain
Next Time:
• Color Vision
• Read Land Article for Thursday Feb 28th
• Go skiing
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