Vision Flashcards
Wavelength (Hue) - Hue (color):
dimension of color
determined by wavelength of light.
Wavelength (Hue) - Wavelength
Wavelength is the distance from
the peak of one wave to the peak of
the next.
Notice the longer waves of red at
the top, and the tighter (shorter)
waves of blue and violet at the
bottom.
Different wavelengths of light
result in different colors picked up
by our retinas.
Intensity (Brightness)
amount of energy in a wave determined by amplitude; related to perceived brightness.
Intensity (Brightness) - Amplitude:
how high each wave
is.
Nearsightedness
A condition in which nearby objects are
seen more clearly than distant objects
because eye is elongated in shape, so
the image focuses before it hits the
retina.
Farsightedness
A condition in which faraway objects
are seen more clearly than near objects
because the eye is shortened and the
image focuses after it hits the retina.
Retina
The light-sensitive inner surface of the eye, containing receptor rods and cones plus layers of other neurons (bipolar and ganglion cells) that process visual information.
Light travels to the back of the retina,
then moves forward, then to the optic
nerve.
Fovea
Central point in the retina, within
which the eyes cones cluster
together… because of the cones
here, there are little color vision in the
farthest periphery of our vision.
Photoreceptors
Rods: sensitive to light
Cones: sensitive to color and fine detail
Bipolar and Ganglion Cells
Bipolar cells receive messages from photoreceptors and transmit them to ganglion cells, which then form the optic nerve.
Cones each have their own bipolar cell.
Multiple rods share one bipolar cell, so their message is not sent as clearly.
Feature Detectors
Nerve cells in the visual cortex that respond
to specific features, like edges, angle, length
and movement.
There are even some feature detectors that
are specifically sensitive to the human face!
Would feature detectors be a sensory or
perceptual experience?
Visual Information Processing
Processing several aspects of the stimulus
simultaneously is called parallel
processing. The brain divides a visual
scene into subdivisions such as color, depth,
form and movement, etc.
Theories of Color Vision
Trichromatic theory (Young-Helmholtz):
Based on
behavioral experiments, Helmholtz suggested that the retina contains
three receptors (cones) sensitive to red, blue, and green colors.
Color Deficiencies (blindness)
Genetic disorder which prevents individuals from
discriminating between certain colors due to a
weakness in or lack of one of the cones
Most common form of color “blindness” is difficulty
distinguishing between red and green
Complete color deficiency does exist but is very rare…it
would be like watching a black and white movie.
Theories of Color Vision
Opponent Process Theory:
Hering, proposed that we process
four primary colors opposed in pairs of red-green, blue-yellow, and
black-white.
