Colour Vision Part 1 & 2

Question 1

What are the three steps to colour perception?

Answer 1

1) Detection
2) Discrimination
3) Appearance

Question 2

Detection: What must happen for color perception to occur?

Answer 2

Wavelengths of light must be detected, and for this we need photoreceptors to convert light into signals in the nervous system.

Question 3

Discrimination: What does the discrimination step involve in color perception?

Answer 3

Discrimination refers to the ability to tell the difference between one wavelength (or mixture of wavelengths) and another. For this, we need neurons that compare inputs from different kinds of photoreceptors.

Question 4

What is the third and final step in color perception?

Answer 4

Appearance: we want to perceive colors to lights and surfaces in the world and we dont want colors to change dramatically in different viewing conditions

Question 5

S-cones: What type of wavelengths are s-cones sensitive to and what are they commonly known as?

Answer 5

: S-cones are sensitive to short wavelengths and are commonly known as “blue cones”.

Question 6

M-cones: What type of wavelengths are m-cones sensitive to and what are they commonly known as?

Answer 6

M-cones are sensitive to medium wavelengths and are commonly known as “green cones”.

Question 7

L-cones: What type of wavelengths are l-cones sensitive to and what are they commonly known as?

Answer 7

L-cones are sensitive to long wavelengths and are commonly known as “red cones”.

Question 8

What determines the response of a single photoreceptor cell?

Answer 8

Determined by the amount of light it receives, regardless of the wavelength of the light. This means that a photoreceptor can’t tell the difference between different colors of light that have the same amount of brightness.

Question 9

What is the problem of univariance?

Answer 9

Refers to the fact that a single photoreceptor in the eye cannot distinguish between different combinations of light intensity and wavelength of light. In other words, if two different colors of light stimulate the same photoreceptor with the same amount of light, the photoreceptor cannot differentiate between them.

Question 10

Why can’t we see different colours in a dimly lit scene?

Answer 10

Our rod cells can’t pick up on these differences because they all respond the same way to light, no matter what color it is. This means that we can only see in black and white under dim light conditions, like moonlight, even though the same colors are still present.

Question 11

How do different cone types allow us to differentiate between wavelengths of light?

Answer 11

While two wavelengths of light may produce the same response in one type of cone, they can produce different responses in other types of cones, allowing us to differentiate between them.

Question 12

What range of wavelengths can produce a unique set of three responses from the three cone types, according to the trichromatic theory of color vision?

Answer 12

Any wavelength from about 420 to 660 nm can produce a unique set of three responses from the three cone types, which can be used as the basis for color vision.

Question 13

How does the combination of signals from the three cone types allow us to see colors?

Answer 13

The combined signal from these three types of cones creates a triplet of numbers for each “pixel” in the visual field, which allows us to see colors.

Question 14

What is the trichromatic theory of color vision?

Answer 14

Based on the idea that color perception is a result of three different cone types in our eyes, each sensitive to a different range of wavelengths, and that the relative activity of these cone types determines our perception of color.

Question 15

What are metamers in color vision?

Answer 15

Metamers are mixtures of different wavelengths that look identical to our eyes.

Question 16

How do long and short wavelength lights mix to produce the same response as medium wavelength light?

Answer 16

The long wavelength light that looks red and the shorter wavelength light that looks green mix together to produce the same response from the cone as does the medium wavelength light that looks yellow.

Question 17

What is needed to match any reference light in color vision?

Answer 17

Three mixing lights are needed to match any reference light in color vision.

Question 18

What is additive color mixture?

Answer 18

A mixture of wavelengths of light.

Question 19

What happens when an additive mixture of blue and yellow light is mixed?

Answer 19

An additive mixture of blue and yellow light will appear white.

Question 20

Why is the result of additive mixture of blue and yellow white?

Answer 20

We see white light because the mixture stimulates all three types of cones in our eyes equally, which our brain interprets as a mix of all the colors we can see which appears as white.

Question 21

What is subtractive color mixture?

Answer 21

Subtractive color mixture is when pigments are combined, absorbing or subtracting certain wavelengths of light and resulting in a new color.

Question 22

What is the neural basis for discriminating between lights with different wavelength compositions?

Answer 22

The nervous system uses the difference in activities of the three cone types, computing two differences: (L-M) and (L+M)-S.

Question 23

What are cone-opponent cells?

Answer 23

Cone-opponent cells are a type of cell found in the retina, LGN, and visual cortex that subtracts one type of cone input from another to create color opponency.

Question 24

How are S-cones involved in color opponency?

Answer 24

In cone-opponent cells in the LGN, S-cones are often pitted against L+M cones in the form of S-(L+M) and (L+M)-S interactions, contributing to the perception of blue-yellow color opponency.

Question 25

What are non-spectral hues?

Answer 25

colors that cannot be created by a single wavelength of light, but rather are created by the combination of multiple wavelengths.

Question 26

What is Opponent Color Theory?

Answer 26

A color theory that explains how our visual system processes color in terms of opposing color pairs, and how these pairs work together to create the full range of colors we see.

Question 27

What is hue cancellation?

Answer 27

A concept for removing or correcting unwanted colors by adding their opposite hue.

Question 28

What are unique hues?

Answer 28

Specific colors that are perceived as distinct and cannot be described as a mixture of other colors.

Question 29

Acromatophisa

Answer 29

Inability to perceive colour

Question 30

What is color assimilation?

Answer 30

The appearance of one color being influenced by the presence of another color,

Question 31

What is an unrelated color?

Answer 31

An unrelated color is a color that can be experienced in isolation, without being influenced by other colors.

Question 32

What is a related color?

Answer 32

A related color is a color, such as brown or gray, that is perceived differently based on the colors around it.

Question 33

What are negative afterimages?

Answer 33

Negative afterimages are optical illusions that occur when your eyes and brain work together to see something that isn’t really there.

Question 34

How does a negative afterimage appear?

Answer 34

In the case of a negative afterimage, the afterimage appears in complementary colors to the original image ( For example, if you stare at a green image for a few seconds and then look away, you may see a red afterimage.)

Question 35

What kind of stimuli produce negative afterimages?

Answer 35

Light stimuli produce dark negative afterimages.

Question 36

What is the adapting stimulus in negative afterimages?

Answer 36

The first colored stimulus is the adapting stimulus, and the illusory color that we see afterwards is the negative afterimage.