Color

Question 1

How much of the electromagnetic spectrum do we see?

Answer 1

between 400-700nm

Question 2

What are photoreceptors?

Answer 2

Photoreceptors are tuned to respond to a particular wavelength/color.

Question 3

What is the problem of univarience?

Answer 3

Two completely different colors elicit the same response.

Changing intensity makes it even worse.

Question 4

What stimuli to photoreceptors respond to?

Answer 4

Photoreceptors respond to both wavelength and intensity.

Question 5

What is intensity?

Answer 5

brightness

Question 6

Can we see light with only one kind of photoreceptors?

Answer 6

NO

Question 7

What are the two type of light levels?

Answer 7

Photopic and Scotopic

Question 8

What is photopic light?

Answer 8

Bright sunlight and indoor lighting.

Stimulates cones and saturates rods.

Question 9

What is scotopic light?

Answer 9

Moonlight, dim indoor lighting.

Stimulates rods, but too dim for cones.

Question 10

What type of photoreceptors respond best to scotopic light?

Answer 10

Rods-

All rods contain the photopigment rhodopsin.
All rods have the same sensitivity to various wavelengths of light.

Question 11

What type of photoreceptors respond best to photopic light?

Answer 11

Cones are active in photopic light.

There are three types of cones, each with different photopigment, sensitive to different wavelengths.

Question 12

What are the three types of cones in trichromacy?

Answer 12

l-cones
m-cones
s-cones

Question 13

What are l cones?

Answer 13

Preferentially tuned to long wavelengths

“red” cones

Question 14

What are m cones?

Answer 14

Preferentially tuned to middle wavelengths

“green” cones

Question 15

What are s cones?

Answer 15

Preferentially tuned to short wavelengths

“blue” cones

Question 16

What is color matching?

Answer 16

• theory is if you have the right shades of 3 colors- (red,green,blue) you can make any color

Question 17

What are metamers?

Answer 17

Different mixtures of wavelengths that look identical

Question 18

What is additive color mixing?

Answer 18

If light A and light B are both reflected from a surface to the eye, your perception is based on the addition of the two.

Question 19

What is subtractive color mixing?

Answer 19

Mix Pigment A and Pigment B.
A absorbs some wavelengths and reflects others.
B absorbs some wavelengths and reflects others.
What you see is what is left after each pigment subtracts some.

Question 20

How do you describe color?

Answer 20

any color can be specified using three numbers

Question 21

What is RGB colorspace?

Answer 21

Defined by the amount of Red, Green, and Blue.

Long, medium, and short wavelength lights.

Question 22

What is HSB Color Space?

Answer 22

Hue: chromatic (color) aspect of light.
Saturation: chromatic strength of a hue.
Brightness: distance from black in color space.

Question 23

What are ‘legal colors’?

Answer 23

Only some color combinations are allowed.

Question 24

What are the legal and illegal color combinations?

Answer 24

Legal”:
bluish-green (turquoise, aqua)
reddish-yellow (orange)
bluish-red (purple)
“Illegal”:
reddish-green
bluish-yellow

Question 25

What is the opponent color theory?

Answer 25

Perception of color is based on the output of three mechanisms, each of them based on an opponency between two colors:

Question 26

What are some of the opponent color?

Answer 26

red-green blue-yellow black–white

Question 27

How do we process color?

Answer 27

Cells in the LGN respond to combinations of signals from retinal ganglion cells.

Question 28

What is a color opponent cell?

Answer 28

Color-opponent cell: A neuron whose output is based on a difference between sets of cones. Same wiring as lateral inhibition.

Question 29

How do neurons in the LGN respond to the Color opponent cells?

Answer 29

Some are excited by M-cones in the center and inhibited by L-cones in the surround (and vice versa): red-green Others are excited by S-cones in the center and inhibited by (M+L)-cones in the surround (and vice versa): blue-yellow.

Question 30

What is selective adaptation?

Answer 30

We can observe opponent-cells using adaptation,

Question 31

What is an afterimage?

Answer 31

A visual image seen after a stimulus has been removed.

Question 32

What is a negative afterimage?

Answer 32

``` An afterimage whose polarity is the opposite of the original stimulus white image → dark afterimage red image → green afterimage blue image → yellow afterimage (and vice versa) ```

Question 33

How many people are effected by color blindness?

Answer 33

8% of male population | 0.5% of female population

Question 34

What are the three types of colorblindness?

Answer 34

protanopia deuteranopia tritanopia

Question 35

What is protanopia?

Answer 35

Absence of L-cones | 1.3% of males, 0.01% of females

Question 36

What is deuteranopia?

Answer 36

Absence of M-cones | 1.2% of males, 0.01% of females

Question 37

What is tritanopia

Answer 37

Absence of S-cones | 0.001% of males, 0.03% of females

Question 38

What is color anomalous?

Answer 38

L- and M-cones that are so similar that they can’t make discriminations.

Question 39

What is a cone monochromat?

Answer 39

Only one cone type; truly color-blind.

Question 40

What is a rod monocromat?

Answer 40

No cones at all.

Question 41

What is cultural relativism?

Answer 41

Basic perceptual experiences (e.g., color perception) may be determined in part by the cultural environment.

Question 42

What is an unrelated color?

Answer 42

A color that can be experienced in isolation.

Question 43

What is a related color?

Answer 43

A color that is seen only in relation to other colors. e.g., brown, gray A “gray” patch in complete darkness appears white

Question 44

What is an illuminant?

Answer 44

The light that illuminates a surface

Question 45

What is color consistency?

Answer 45

The tendency of a surface to appear the same color under a fairly wide range of illuminants.