Colour Flashcards
What is colour perception
Bring lots of contrast to everything
Very useful
What is colour vision related to
Properties of opsins in cones —> sensitive to diff wavelengths
Name the cones that see diff types of light
S cones for short wavelengths = blue
M cones for medium wavelengths = green
L cones for long wavelengths = red
What is inverted spectrum
Hypothetical concept pertaining to philosophy of colour - of 2 ppl sharing their colour vocabulary and discriminations
Colours one sees = qualia = systemically different from colour other person sees
What is qualia
Subjective, first person experience of perception and sensation that are inherently personal and difficult to communicate or measure
Represent what it is like aspect of seeing world
Disproves physicalist view of world
= how things perceived subjectively
Colour = something mind makes up, not actually a colour, wavelengths projected -> brain sees colour
Name exs of qualia
Redness of red
Bitterness of coffee
Pain of a headache
Sound of violin
Marys room thought experiment = set up - Mary’s confinement
Proves that qualia matters
Marys knows everything about science of colour vision - 3rd person perspective
Lives whole life in black and white room - has only black and white materials and views world through black and white monitor
Has never experienced colour first hand
Marys room thought experiment = her knowledge
Mary learns everything about physical processes of colour vision = how light waves of certain wavelengths stimulate photoreceptors in retina - how signals processed in brain - how colour’s perceived
= Mary knows all about physical facts of colour vision
Marys room thought experiment = key moment
One day = Mary released form black and white room = sees colour for first Tim
= learns something from 1st person perspective = learns what colour feels like
Marys room thought experiment = philosophical question
Does Mary learn something new when she experiences colour for the first time
= if she does = means there is more to knowing about colour than the physical facts = subjective experience of qualia
Learned qualia of colour - learned something nonphysical when got out of room
Marys room thought experiment = implications
Against Physicalism (the idea that only physical/material things exist):
* If Mary learns something new upon experiencing color, it suggests that physicalism is incomplete because it cannot account for the subjective, experiential knowledge (qualia) of seeing color.
In Favor of Dualism or Non-Physicalist Views:
* The experiment supports the idea that subjective experiences (qualia) are a separate kind of knowledge that cannot be fully explained by physical facts alone.
Conclusions = idea that everything physical/material is limited - there are things in this world that are purely mental = how things feel to us
What does qualia lie at the heart of
Lie at heart of hard of problem of consciousness
Describe the hard problem of consciousness
Chanllenge remains in exploring why and how neural processes give rise to subjective experience
Questions how mere electrochemical activity in brain translated to lived experiences
No widely excepted framework for bridging the gap between neural activity and emergence of qualia = making it one of the most profound mysteries in philosophy and cognitive science
What is basis of colour perception - explain fully
Cone cells
Cannot Perceiev colour based on activity of just one type of cone cells
Did types cones more sensitive to a specific wavelength
Describe principle of univariance
Infinite set of different wavelength x intensity combos can elicit same response from single type photoreceptor
= so one type of photoreceptor cannot make colour discriminations
How’s does each photoreceptor respond to light
Each cone cell in retain responds to light by generating signal proportional to amount of light it absorbs
Why can’t a single photoreceptor distinguish colour
Bc = bright but less preferred wavelength = weakly absorbed colour at high intensity
Dim but highly preferred wavelength = strongly absorbed colour at low intensity
= give same response
Cannot distinguish between blue and red or between green and yellow
What do we need to see colour
Need to have more than one photoreceptors reacting
Bc many brightness levels irl = level of activity of cone driven by any combo of intensity and wavelength
Describe what is needed for every wavelength
Need 3 cones
For every wavelength = particular combo for activity across the 3 types of cones - remains constant for diff intensities
= resolves problem of univariance and allows colour perception - pattern unaffected by intensity - relative degree of activity perserved (even if cones shifted up)
Describe what happens when missing m cones - gen
Every frequency above s cone limit only encoded by l cones = can produce same response for diff wavelengths/intensity combos
But colours to left perserved
Describe what happens when missing m cones - graph
Cannot see indigos
- only l cones on left = colour only encoded by 1 cone = cannot discriminate = problem of univariance = Cannot tell difference between red and green
How many ppl colour blind
8% males
0.5% females
Have some form colour deficiency = blindness
More common in males bc colour normally caused by recessive gene on X chromosome - most women have other x to compensates
Define colour anomalous
Term for “colour blindness”
Most colour blind ppl can still make discriminations based on wavelength - just diff from norm
Describe deuteranope
Due to absence m cones
Describe protanope
Due to absence l cones (everything after s cones appears yellowish = affects red and green)
Describe tritanope
Absence s cones
(Cannot see blue and yellow)
Describe cone monochromat
Has only one type of cone
= truly colour blind, rare
Which types of colour anomalies are similar
Response properties of l and m cones v similar = protanope and deuteranope
(Also the most common types)
What is trichomacy
Pshycially stduying light
Theory taht the colour of any light is defined in visual system by relationships of 3 numbers - outputs of 3 receptor types now known as 3 cones
= 3 colours required to march any other colour - rgb, 2 were sometimes insufficient = cannot recreate some colours
Thomas young, Hermann con Helmholtz
What do we see generally
Do not see pure wavelengths - like light that comprises of one wavelength
But we see mixture fo waveslenghts
Entirely determined by relative level of activity of 3 cones = pattern fo response, does not matter how we get there
What happens when mix 2 pure wavelengths
Ex = green and violet = combo of activity of m and l cones identical to combo resulting from pure wavelength in cyan frequency
- cannot distinguish 2 = all look cyan
Define metamers
Diff mixtures of wavelengths that look identical = more generally = any pair of stimuli that are perceived as identical in spite of physical differences
Perceived as same colour = metamers of each
Metamers ex
480nm = metamers for 534 + 270 nm
Cyan=480
Green =534 and purple = 370 = looks bright ere and produces same pattern as cyna
Name the 2 types of colour mixing
Additive
Subtractive
Define additive colour mixing
Process of creating colours by combing diff wavelengths of light
What primary colours in additive colour mixing
Red
Green
Blue
additive colour mixing = if mix all what produced
At full intensity = produce white light
Like colour displays for tv screens and computer monitors
Define subtractive colour mixing
Process of creating colours by removing - absorbing certain wavelengths of light
What primary colours in subtractive colour mixing
Cyan
Magenta
Yellow
subtractive colour mixing = if mix all what produced
Absorb more light and produce darker colour = all 3 mix to form black
Basis of printing, painting, pigments
Describe ex of subtractive colour mixing
Yellow pigment = absorbs blue and reflects red, oranges, yellow, green
Cyan = absorbs red organge yellow an reflects blue and green
So add together = get green, bc green only one in common
What does mixing colour do
Produces colours not on spectrum visible light = doesn’t exist
Define nonspectral hues
Hues that can arise only from mixtures of wavelengths
What is purple
No purple in spectrum = produced by combo of s m l cones
= activates s and l cones but not m
Nonspectral hue = only by mixing diff types light
dEscribe ex nonspectral hues
Purple - colours in this range not associated with specific wavelength —> produced by activity in l and s cones but not m cones - specific mixture of light wirh lot of long and short wavelengths
What is opponent colour theory
4 unique hues/pure colours
Some colour combos Legal and others illegal
Name legal colours
Bluish green = cyan
Reddish yellow = orange
Blueish red = purple
Name illegal colours
Reddish green
Blueish yellow
- cannot really have these
Describe how colours are processes in opponent process theory
Supports opponent process theory = colours processes in opposite pairs
Red vs green
Blue vs yellow
Etc
Define hue cancellation experiments
Method used to determine opponent colour processing
Participants adjust amount of an opponent colour - like add green to cancel our red
Until no trace of original hue remains - helps map sensitive of visual system to diff colour opponencies - red green, blue yellow
Have to shine opponent colour
Ex hue cancellation experiments
If blue reddish = add green to make perfectly blue
If blue reddish = add green to make perfectly blue - if add too much = will look greenish blue
To remove green = add more red to be perfectly blue again
What are pure colours
At certain transition points = get pure colour
4 spots associated with unique hues - transition points = pure colours
Unique blue, yellow, green, red
What is informative for opponent colour theory
Cones in general v sensitive to itensity of light for wide range of wavelengths
Absolute level of activity for a particular cone type = uninformative
Difference of activity between types of cone s= VERY informative
What computes red vs green
[L-M]
[M-L]
What computes blue vs yellow
[L + M] - S
S - [L + M]
What encodes general brightness
[L + M + S]
What combo oof cones is uninfomative
[L-S] OR [S-L] AND [M-S] OR [S-M]
Bc m and l are so simialr and are not used
Describe organization of cones for opponent colour theory
Centre surround organizing - ganglion cells
Green and red cones = undifferentiated = add up = makes yellow
Describe dress phenomenon
50% = blue or black, 20-30% - white/gold
Visual system does not care about exact wavelength - just about enhancing contrast
So some ppl see diff bc of discounting illuminant
Assume yellow illuminant = so dress looks blue
Assume blue illuminant = dress looks white
Depends on what ppl interpret - visual system just wants to increase contrast
Describe colour constancy = gen
Visual system guesses illumiant and discounts it
Describe colour constancy = define
Brain estimates light source and adjusts perception to maintain stable colours
= colour constancy (even when inside/outside colours look the same)
= allows us to discount influence of illuminant and focus on true colours of objects
Describe colour constancy = ex
Illumiant a = like white light - along with surface = resembles it
But with illuminant b = with short lambda = will not look like surface but wont matter
Guess average wavelength that is illluminating science and subtract from light reaching retina
