L5 - colour vision

Question 1

what is colour perception?

Answer 1

allows distinction between surfaces of the same brightness

Question 2

What does isoluminant mean?

Answer 2

same brightness

Question 3

What does achromatic mean?

Answer 3

without colour

Question 4

what are the physical properties of colour perception?

Answer 4

wavelength + intensity

Question 5

What are the 2 functions of colour perception?

Answer 5

Signalling e.g., yellow bananas indicate ripeness

Detection e.g., picking cherries is easier with colour perception as some objects stand out fur to their colour

Question 6

What wavelength does blue have?

Answer 6

450-490 nm

Question 7

what wavelength does green have?

Answer 7

500-575 nm

Question 8

what wavelength does red have?

Answer 8

620-700 nm

Question 9

What has to happen for white to be produced?

Answer 9

A mix of all wavelengths

Question 10

what is black?

Answer 10

an absence of light

Question 11

what is reflectance?

Answer 11

objects are seen due light reflection

e.g., a red apple reflects red light and absorbs other colours, making it appear red to our eyes

Question 12

What does a reflectance curve do?

Answer 12

shows the composition of light reflected by an object.

Question 13

what’s chromatic light?

Answer 13

Light that has colour, it consists of specific wavelengths that are. more prominent that others, giving it a distinct hue.

e.g., The light from a blue LED is chromatic light because it is predominantly blue in colour

Question 14

what’s monochromatic light?

Answer 14

Light that consists of a single wavelength or colour

e.g., laser light is often monochromatic because it emits light at a specific wavelength.

A red laser pointer emits monochromatic light at a wavelength around 650 nm, appearing as pure red.

Question 15

What is achromatic light?

Answer 15

Light that has no colour –> includes shades of white, gray and black.

No hue –> doesn’t favour any wavelength

e.g., white light from standard light bulb as it contains all wavelengths of visible in equal measure.

Question 16

what’s additive colour mixing?

Answer 16

the process of creating new colours by combining different colours of light

e.g., using light in the 3 primary colours can be used in various ways to create other colours incl combining all of them to produce white light.

Question 17

what’s subtractive mixing?

Answer 17

the process of creating colours by combining different pigments, dyes or inks, each of which absorbs (subtracts) certain wavelengths of light + reflects others

e.g., using light in colours cyan, magenta and yellow removes wavelengths from white light - producing new colours.

Mixing these colours together theoretically results in black

Question 18

What are the 3 types of cone photoreceptors

Answer 18

S-cones: maximal absorption at short wavelengths (blue)
M-cones: maximal absorption at medium wavelengths (green)
L-cones: maximal absorption at long wavelengths (red)

Question 19

What does density refer to in cone photoreceptors

Answer 19

cones are concentrated around the fovea - resulting in poorer colour discrimination in the periphery.

Question 20

What is opponent process theory?

Answer 20

Theory colour vision that explains how colours are processed at a neurological level after being detected by the cone photoreceptors in the retina.
Proposed by Ewald Hering

Question 21

What are the 3 types of colour deficiencies?

Answer 21

Protanope - missing long wavelengths
Deuteranope - missing medium wavelengths
Tritanope - missing short wavelengths

Question 22

What’s colour constancy?

Answer 22

the ability to perceive the colour of an object consistently under varying lighting conditions.