Download The eye and color notes (1)

Color Blindness
• http://www.iamcal.com/misc/colors/
Vision
• 4 steps to vision
– Gather light into our eye.
– Light is channeled to the back of the eye.
– Transduction occurs
– Information goes to occipital lobe.
• Transduction: The conversion of one form of
energy into another.
What is Color?
• Color does not exist in our world. Your eyes
make color exist.
• What you see if energy. To be visible the light
must be the appropriate wavelength.
The Eye
Eye Parts
• Pupil: Adjustable opening in the center of the
eye where light enters.
• Iris: a ring of muscle tissue that forms the
colored portion of the eye around the pupil.
• Lens: structure behind the pupil that changes
shape to help focus images.
• Retina: The light-sensitive inner surface of the
eye, contains receptor rods and is the area
where information begins to be processed.
Eye Parts
• Rods: retinal receptors that detect black, white, and
gray.
• Cones: retinal receptor cells that are concentrated near
the center of the retina. Detect fine detail and give rise
to color sensations.
• Optic Nerve: nerve that carries neural impulses to the
brain.
• Blind Spot: The point where the optic nerve leaves the
eye. (Creates spots in vision you can not see)
• Fovea: Central area of focus. Cones cluster in this area.
How does the brain process visual
information?
Feature Detection
• David Hubel and Torsten Wisel showed us in
1979 how neurons in the occipital lobe receive
information from ganglion cells in the retina.
• Feature detectors:
– Nerve cells in the brain that respond to specific
features of the stimulus. (shape, angle,
movement)
Parallel Processing
• Parallel Processing is how our brain processes
information.
– Parallel- doing multiple things at once.
– Ex. We process color, motion, form, and depth of
an object all at once.
Young-Helmholtz Trichromatic (threecolor) theory
• Trichromatic theory:
– Our retina contains three different color
receptors—one most sensitive to red, one to
green, one to blue. These three receptors can
produce the perception of any color.
Opponent-process theory
• The theory that opposing retinal processes
(red-green, yellow-blue, white-black) enables
color vision.
• Creates an afterimage effect.
– An image you see after staring at an image.
Opponent-Process Theory
Demo
• Demo:
– You can demonstrate this for yourself by staring at
the red dot in the middle of the image below for
30 seconds without letting your eyes drift from
the center; then look at a blank white sheet and
you will see the image with a more familiar set of
colors. (It may take a while for the image to
develop).