Colour principles

Question 1

Visible light

Answer 1

Light that we are able to perceptualise
380-760nm
Part of the electromagnetic spectrum
Light consists of wavelengths.

Question 2

Electromagnetic spectrum

Answer 2

continuum of wavelengths
Short wavelengths make up blue light
Long wavelengths make up red light

Question 3

Eye structure

Answer 3

Cornea
Pupil
Lens
Retina
Optic nerve - makes up our ‘blind spot”

Question 4

Accomodation

Answer 4

automatic changing the shape of the lens to focus light.

Question 5

Retina

Answer 5

Made up of cones and rods, bipolar cells and ganglion cells contains fovea = where visual activity is greatest, has the most cones
connecting cells = amacrine and horizontal cells

Question 6

Rods and cones

Answer 6

specialized nerve cells that contain light-sensitive chemicals called visual pigments that generate an electrical response to light.
cones= functions in bright light and colour perception. Sensitive to Short Medium and Long wavelengths
rods= functions in dim light

Question 7

Bipolar and ganglion cells

Answer 7

merge the input arriving from the rods and cones.
Each ganglion cells corresponds to a group of rods or cones = receptive field

Question 8

Theories of colour perception

Answer 8

Trichromatic and opponent

Question 9

Trichromatic theory

Answer 9

Presumes that colour perception is a function of the relative stimulation of the three types of cones (blue, green, and
red)
If only one type of cone is stimulated, that colour is perceived
Perception of other colours is a function of the relative ratios of stimulation - yellow light would stimulate green and red cones, and so yellow would be perceived.

Question 10

Opponent-process theory

Answer 10

colour perception is based on a lightness– darkness channel and two opponent colour channels: red–green and blue–yellow. Presumes colours within each opponent colour channel work in opposition to one another
The actuall way our eyes work.

Question 11

Simultaneous contrast

Answer 11

Induction refers to when the perceived colour of an area is affected by the colour of the surrounding area, considered to emerge because of the
receptive fields.

Question 12

Colour vision impairment
(colour blindness)

Answer 12

groups are distinguished based on the number of colours that
must be combined to match any given colour
The most common problem for both groups is distinguishing between red and green

Question 13

Colour vision impairment types

Answer 13

Anomalous Trichromats (use 3 colour cones) - some difficulty in distinguishing colour
Dichromats (use 2 colour cones) - colours cannot be distinguished.

Question 14

Hypotheses for colour vision impairment

Answer 14

• a change in the colours to which cone cells are sensitive
• changes in one of the opponent-process channels (normally the red–green)

Question 15

Subgroups of colour vision impairment

Answer 15

• protanomalous and deuteranomalous for anomalous trichromats
• protanopes and deuteranopes for dichromats

Question 16

Protanomalous

Answer 16

• can have all three cone types, but their L (long wavelength) cones are less sensitive to red light than they should be
• Red may appear as dark gray, and every colour that contains red
  may be less bright

Question 17

Deuteranomalous

Answer 17

can have all three cone types, but their M (medium wavelength)
cones are less sensitive to green light than they should be
* Mostly see blues, yellows and generally muted colours

Question 18

Protanopes

Answer 18

are presumed to be missing red - L cones are missing. So, one
cannot perceive red light
* Colours are seen as shades of blue or gold
* May easily confuse different shades of red with black and confuse dark brown with dark shades of other colours, including green, red or orange

Question 19

Deuteranopes

Answer 19

• are presumed to be missing green - M cones are missing.
• Cannot perceive green light. Mostly see blues and golds.
• May confuse some shades of red with some shades of green and also confuse yellows with bright shades of green

Question 20

Rainbow colour scheme in cartography

Answer 20

Causes data distortions
Is highly misleading
Transition between colours in not seamless.
Some colours stand out more than others can distort the statistics.
vision impairments or colour blindness may find it impossible or inaccurate to read the data given in a rainbow colour scheme.

Question 21

Accommodating colour vision impairment in colour shemes

Answer 21

can be accommodated by colour schemes that suit red- or green-blind dichromats and green colour-blindness in mind.
Data graphics can be designed with the most severe kinds of red and green colour-blindness in mind.
Sequential, diverging and qualitative colour schemes have been tried and tested for print and online display and evaluated for legibility by readers with colour-deficient vision.

Question 22

Sequential colour scheme

Answer 22

Display data with non-midpoint critical values by using sequential colour schemes:
* The most popular colour schemes used in thematic mapping
* Excellent for demonstrating the order of data values

Question 23

Diverging colour scheme

Answer 23

Uses two complementary colour schemes that diverge from a
common hue to display diverging data
Instead of showing a single progression, however, they visualize the distance of all values from a critical point
work well for depicting data with critical middle value or class

Question 24

Qualitative colour scheme

Answer 24

Demonstrate differences, but not order, between map classes
* Often used when creating maps of political boundaries, or to create categorical choropleth maps and most common in creating land use or land cover maps
* Used for nominal, but, not ordinal or ratio data

Question 25

When anomalies are equally
represented the colour scheme is..?

Answer 25

• Perceptually uniform
• Perceptually ordered
• Colour-vision deficiency friendly
• Readable in black & white print

Question 26

Visual processing system

Answer 26

Information leaving the eyes via the optic nerves crosses over at the optic chiasm; up to that point, information from each eye is separate, but pathways beyond this point contain information from both eyes.
Beyond the optic chiasm, each pathway enters the lateral geniculate nucleus = LGN.

Question 27

primary visual cortex

Answer 27

Visual information interpretation begins here, the first place where all of the information from both eyes is handled

Question 28

Interpretation of visual information

Answer 28

Research efforts found three kinds of specialized cells in the primary visual cortex:
* simple cells
* complex cells
* end-stopped cells

fMRI utilizes an MRI scanner, which generates strong magnetic fields
that pass through the human body - may provide insight to the issue of how the brain handles a map.

Changes in metabolic demands of nerve cells are an indication of which area of the brain is activated.

Question 29

Simple cells

Answer 29

respond best to lines of particular orientation

Question 30

Complex cells

Answer 30

respond to bars of particular orientation that move in
a particular direction

Question 31

end-stoped cells

Answer 31

respond to moving lines of a specific length or to
moving corners or angles