read land’s article about color vision for tuesday next week
TRANSCRIPT
• Read Land’s article about color vision for Tuesday next week.
Midterm 2
November 2nd and 3rd
Covers everything about vision
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?
“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
The Correspondence Problem
• What is the Correspondence Problem?
The Correspondence Problem
• What is the Correspondence Problem?
– How does the brain know what contours to match up…what images correspond?
The Correspondence Problem
• Maybe shape analysis is done first to make it easier to match up corresponding parts
How did Bela Julesz prove this model wrong?
The Correspondence Problem
• Bela Julesz tested this with random-dot stereograms
• No contours or form available in monocular image!
• Surface in depth still visible
Left Eye Right Eye
The Correspondence Problem
• A different model must be adopted:
The Correspondence Problem
• A different model must be adopted:Visual system can extract form by matching up individual elements (dots) in an image, computing disparity between them, and finding the most likely surfaces.
Might this involve top-down mechanisms? How could you test that hypothesis?
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
recovers 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