S&P Exam 2: Chapter 9: Perceiving Color

Name the three functions of color vision?

1. Classify and identity objects

2. Perceptual organization

3. Evolutionary advantage (be able to detect poisons or predators)

What did Newton’s Light Experiments reveal?

Revealed that white light is actually a mixture of all colors in the visible spectrum, rather than a pure, simple substance.

Through prism experiments, he demonstrated that color is produced from light rays that can be separated

True/False: Color perception is related to the wavelengths of light that enter our eyes

True

When do chromatic colors or hues occur?

when some wavelengths are reflected more than others

When do achromatic colors occur?

light is reflected equally across the spectrum

Name achromatic colors (3)

white, black, and gray tones

Name chromatic colors (4)

red, yellow, green, blue

Short wavelengths =

blue

Medium wavelengths =

green

Long and medium wavelengths =

yellow

Long wavelengths=

red

Long, medium, and short =

white

What is selective reflection?

some wavelengths reflect off objects more than others

What is selective transmission?

transparent objects selectively allow wavelengths to pass through

What does subtractive color mixture involve?

mixing PAINTS with different pigments

In subtractive color mixture only wavelengths reflected by ______ are perceived.

Both

Blue paint reflects all _______wavelengths and reflects some _______wavelengths. Blue paint absorbs all ______ wavelengths.

short and medium

long

Yellow paints reflects some _______wavelengths and reflects some _____ wavelengths. Yellow paint absorbs all _____ wavelengths.

medium and long

blue

A mixture of blue and yellow paint reflects some ______ wavelengths. A mixture of blue and yellow paint absorbs all ________ wavelengths and all _____ wavelengths.

medium

short and long

What does additive color mixture involve?

mixing light of different wavelengths

In additive color mixture, _____ wavelengths are reflected for the observer to perceive.

all

What is hue?

the experience of a chromatic color

What is value?

the lightness of a color

What is saturation?

the intensity of a color

What are the perceptual dimensions of color? (3)

hue, value, saturation

What is the spectrum range for visible light?

400-700

What is the trichromatic theory of color vison?

three different receptor mechanisms are responsible for color vision.

(blue: short, red: long , and green: medium)

Where were the results of the Spotlight Color Matching Experiments?

Participants could only match the color with more accuracy when using red, green, and blue lights rather than less than three lights

What is the range for each wavelength (short, medium, and long)

short- 419 nm

medium 531 nm

long 558 nm

What are metamers?

colors that are perceptually similar despite having different physical wavelengths

What are monochromats?

people who have no function cones and rely on rods for vision

-rare and hereditary

Why can’t one receptor type lead to color vision?

• Absorption of a photon causes the same effect, no matter what the wavelength is.

• Any two wavelengths can produce the same response by varying their intensities.

What is the principle of univariance?

once a photon of light is absorbed by a visual pigment molecule, the identity of the light’s wavelength is lost

What are dichromats?

those who have two receptor types

can perceive some colors

What are trichromats

those who have three receptor types

can perceive many more colors

What are the three types of Dichromats?

Protanopia

Deuteranopia

Tritanopia

What is Protanopia?

X-inherited

missing LONG wavelength pigment

What is Deuteranopia?

X-inherited

missing MEDIUM wavelength pigment

What is Tritanopia?

VERY RARE

Missing short wavelength pigments

What is an anomalous trichromat?

those who have three receptors, but not at good at discriminating between wavelengths that are close together

What is an unilateral dichromat?

those who have trichromatic vison in one eye (3 receptors) and dichromatic (2 receptors) in the other

What is Tetrachromacy?

a rare genetic condition where individuals, typically women, possess a fourth cone cell in their eyes, enabling them to see up to 100 million colors

What is the Opponent-Process Theory of Color Vision

opponent neurons (neutral circuits) receive excitatory and inhibitory inputs from the three cone types

explaining why we cannot see "reddish-green"

What are the opposing color pairs according to Opponent-Process theory of Color Vision?

red v green

blue v yellow

black v white

True/False: Opponent neurons determine the difference between the receptor responses to different wavelengths.

True

Single-opponent cells detect color….

color within regions

Double-opponent neurons detect…..

boundaries between colors

What are afterimages and how do they support the Opponent-Process Theory of Color Vision?

According to the opponent-process theory, color afterimages are negative afterimages caused by the fatigue of specific retinal ganglion cells after prolonged exposure to a color. When looking away at a neutral surface, the fatigued cells send weak signals, causing their opposite color (red-green, blue-yellow, or black-white) to dominate perception

How does color vision of tetrachromats differ from that of trichromatic?

• Enhanced Color Differentiation: Tetrachromats can see millions more shades of color, finding differences in hues that look identical to a trichromat.

• Higher Sensitivity to Color Distinctions: They may be better at distinguishing variations in color in low-light conditions.

• Unique Color Blends: They may perceive colors in yellow, orange, and green shades as more distinct, perceiving "extra" color bands in the spectrum.

How to combine Opponent process theory and Trichromatic theory?

Trichromatic theory applies to retinal cones

Opponent process applies to the neural response for cells further in the color perception process

True/False: There is a single brain module for color perception

False

Cortical cells in V1 and V4 respond to some wavelengths or have _______responses

Opponent

What is color constancy?

perception of colors as relatively constant in spite of changing light sources

What is chromatic adaptation?

Prolonged exposure to chromatic color leads to receptors:

– “Adapting” when the stimulus color selectively bleaches a specific cone pigment

– Decreasing in sensitivity to that color

Adaptation occurs to light sources, leading to…

color constancy

What is partial color constancy?

Your brain adjusts to new lighting (adaptation) so colors seem relatively stable, but not perfectly so. When lighting changes, an object's perceived color shifts slightly, but this shift is smaller than if your eyes hadn't adapted at all, allowing you to still recognize the object's true color.

How does chromatic adaptation explain the color constancy of objects in different sources of light (sunlight, tungsten light, and LED light)?

Chromatic adaptation maintains color constancy by adjusting the sensitivity of the cones to the prevailing light source, allowing colors to appear consistent across varying conditions.

• Sunlight (Daylight): Sunlight has a relatively balanced spectrum. The visual system operates under a standard neutral setting.

• Tungsten (Incandescent): This light is heavy in red/yellow wavelengths. The eye reduces its sensitivity to these long wavelengths (cone adaptation) and increases sensitivity to blue/green, canceling out the warm tint.

• LED Light: LED light quality varies (blue-tinted or warm). The eye quickly adapts to the specific spectral output of the LED to normalize the color experience

Why can’t we see color in the dark?

We cannot see colors in the dark because our eyes rely on two different types of receptors, and the ones responsible for color (cones) require bright light to function. In low light, our eyes switch to rods, which are highly sensitive but only detect shades of gray, black, and white.

What is the Hansen et al. Color Constancy Experiment reveal?

shows that color constancy is also influenced by memory and associations of object color with our experiences of them.

The amount of light reaching the eye depends on…. (2)

illumination

reflectance

What is illumination?

total amount of light that is striking the object’s surface

What is reflectance?

proportion of this light that the object reflects into our eyes.

Lightness constancy is related to the perception of lightness determined by..

reflectance

Black objects reflect ___ % of light

5

White objects reflects ___ to ____% of light

80-95%

What is the ratio principle?

two areas that reflect different amounts of light look the same if the ratios of their intensities are the same

When does the ratio principle work?

when objects are evenly illuminated

What are reflectance edges?

edges where the amount of light reflected changes between two different surfaces

What are illumination edges?

edges where the lighting on a single surface changes

The ____ of shadows signals an illumination edge?

penumbra

Information about the _______ of a surface affects our perception of lightness.

orientation

True/False: Light waves are colorless

true

True/False: Physical energy in the environment has perceptual qualities.

False

What is the penumbra?

the fuzzy border at the edge of a shadow that signals where the illumination edge is

What did Bornstein et al (1976) reveal about infant color vison?

Babies do not have great perception of shade differences between colors'

• When infants are shown green for a long time, then shown either a blue and a light green, they looked longer at the blue, indicating they saw more difference in the blue than the lighter green