3.3-3.4: Visual Anatomy + Perception

HUE (color): dimension of color determined by wavelength of light.

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.

INTENSITY (BRIGHTNESS)

INTENSITY: amount of energy in a wave determined by amplitude; related to perceived 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.

FARSIGHTED: 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 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

• In this image, notice what the next cell that the rods connect to versus the cones… what’s different?

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 cells
• multiple rods share one bipolar cell, so their 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 more some feature detectors that are specifically sensitive to the human face!

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.

Opponent Process Theory: Hering, proposed that we process four primary colors opposed in pairs of red-green, blue-yellow, and black-white.

COLOR DEFICIENCIES:

• 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.