Vision

cornea

transparent outer covering of the eye

pupil

the adjustable opening in the center of the eye through which light enters

iris

ring of colored muscle tissue that controls the size of the pupil opening (when such light enters the eye)

lens

transparent structure behind the pupil changes to help focus images on the retina

retina

the light-sensitive inner surface of the eye that contains the receptor rods + cones plus layers of neurons

fovea

(point of central focus in the retina) contains most of the eye’s cones

accommodation

process in which the lens changes the curvature + thickness.

helps the light rays on the retina + to see clearly

nearsightedness (myopia)

a condition where nearby objects are seen more clearly than distant ones b/c the eye is elongated in shape, so the image focuses before it hits the retina

farsightedness

a condition where faraway objects are seen more clearly than near objects b/c the eye is shortened and the image focuses after it hits the retina

retina

light travels to the back of the retina, then moves forward, then to the optic nerve

fovea

the central focus point in the retina; where the cones cluster together…b/c of cones here, there is little color vision in the farthest periphery of our vision

cones

sensitive to color and fine detail

rods

sensitive to light

after light is received in the cones and rods, it goes next to the….

bipolar cells → ganglion cells → optic nerve

wavelength

the distance from the peak of one wave to the peak of the next

hue (color)

dimension of color determined by wavelength of light

amplitude

the height of the wave

intensity

amount of energy in a wave determined by the amplitude; related to perceived brightness

• greater — brighter

• smaller — duller

why do wavelengths of light result in….

different colors picked up by our retinas

visual cliff

• 1960 — Eleanor Gibson + Richard Walk

• created device to test children’s (infants) depth perception

• most infants did not go onto clear part

  • d.p = Yes!

• Why: nature + nuture

Young-Helmholtz Trichromatic Theory

suggest that the retina contains 3 receptors (codes) sensitive to red, blue, and green

red green blue

Opponent-Process Theory

Hering proposed that we process 4 primary colors opposed in pairs of red-green, blue-yellow, and black-white

color blindness

abt. 1 in every 50 people are color blind — more common in males (defect is genetically sex-linked)

most people with this vision aren’t actually blind to all colors. they simply lack functioning red-sensitive or green-sensitive cones — or in some cases, both

feature detectors

nerve cells in the visual cortex that respond to specific features of a stimulus, such as shape, angle, and movement

• some of these are specifically sensitive to the human face!

parallel processing

processing several aspects of the stimulus simultaneously

• brain divides a visual scene into subdivisions such as color, depth, form, + movement, etc

monocular cues

depth perception that requires ONE eye (more limited but still possible)

interposition

the partial blocking of one object by another object, leaving the viewer with the perspective that the blocking object is closer

linear perspective

parallel lines appear to converge at a vanishing point on the horizon

the ore the lines converge, the greater their perceived distance

relative size

if 2 objects are similar in size, the object that looks the largest will be judged as being the closest to the observer

texture gradient

when you’re looking at an object that extends into the distance, such as a grassy field, the texture becomes less and less apparent the farther it goes into the distance

as you look out over the scene, the object in the foreground have a much more apparent texture

binocular cues

we use BOTH of our eyes help us judge distance

convergence

when two eyes move inward (toward the nose) to see near objects, and outward (away from the nose) to see far away objects

the more eyes turn inward, the closer we perceive the object to be

retinal disparity

each eye sees a slightly different image b/c they are about 6 cm. apart (on avg.)

Your brain puts the 2 images it receives together into a single 3-dimensional image