perception-colour vision anomalies

Question 1

what happens in your brain when an image is represented

Answer 1

-signals go to your eye from your brain, and you will have an amount of signals from blue, green and red receptors going into your brain
-you can represented the total amount of signal from red green and blue going into your brain in the systematic plot(look at slides)
-the nervous system can look at the red and green and look at the difference and minus one from the other
-it can also add them up (therefore its black and white)

Question 2

what does the the triangle in a cie diagram represent

Answer 2

-the triangle represents all the colours you can produce in that specific device , so any colours that fall outside the triangle
-if triangle covers most of the diagram, that device will represent as true a colour as it is on the device

Question 2

trichromacy and trivariance

Answer 2

-human vision is trichromatic i.3 we have 3 colour processes (red,green,blue)
- (after getting the signal it is transferred into 3 opponent processes) subsequent processing is trivariant, i.e two opponent colour channels and one brightness channel
-the opponent colour channels are red/green, yellow/blue
-the opponent brightness channel is light/dark (black/white)

Question 2

how do we measure these colours
-CIE chromaticity diagrams (look at slides)

Answer 2

-every colour you could imagine is on this diagram
-you can calculate the coordinates of a colour and those co ordinates can show on this diagram

Question 3

abnormalities of colour vision
-congenital
-acquired

Answer 3

congenital- (present from birth) encoded in genetic makeup
acquired - those with normal colour vision develop partial or total loss of colour vision

Question 3

munsell colour system
hue
value
chroma

Answer 3

hue- is the quality that distinguishes colours
value (brightness) is related to the intensity of light
chroma (saturation) distinguishes pale from vivid

Question 4

what is it called if someone’s photoreceptors dont work

Answer 4

-we have 3 photoreceptors, they either work well,normal or not well
-if all 3 aren’t working well, we can them anomalous and they all become anomalous trichromat

Question 5

what happens if somebody is missing a colour photoreceptor

Answer 5

-if someone has 3 (all) photoreceptors they are trichromat, if they have 2 they are dichromat, if they have one they are monochromatic

Question 6

anopia

Answer 6

if you are blind to something - you dont see it

Question 7

names for missing certain photoreceptors

Answer 7

-1 (pro)long -red
,2) (du) medium- green
3) (tri) short -blue
-if you cant see the red one, its called protanopia
-if green one is missing - dutanopia
-if blue one is missing tritanopia

Question 8

terms for anomalous photoreceptors (photoreceptors that dont work properly)

Answer 8

protanomally
deuteranomally
tritanomally

Question 9

how does anomalous trichromacy occur

Answer 9

-occurs when all three cone types are present but one has an abnormal absorption curve. the severity of the anomaly depends on how abnormal is the absorption.
-thus there are simple anomalous observers and extreme anomalous observers

Question 10

define dichromatic colour deficiency

Answer 10

-is caused by the absence of either L,M, or S cones leading to protanopia , deuteranopia and Tritanopia

Question 11

rod or cone monochromacy

Answer 11

-where there is only one photoreceptor type present, so there is no colour perception

Question 12

graphs of
-normal trichromat
-anomalous trichromat
-protanope, deuteranope and tritanope

Answer 12

look at slides
-anomalous one has all 2 however the green one is shifted
-protanope-red curve was missing
-deuteranope - missing the green curve
-tritanope - missing the blue curve

Question 13

how do
-protanopes
-deutranopes
-tritanopes
view the world

look at the slides

Answer 13

-protanope - dont really see pinky /red (only see yellows to blues in the colour spectrum)
-deuteranope - same as protanope (minor variations) (blues to yellows)
tritanope - dont see blues (colour spectrum looks green to reds)

Question 14

cone monochromats
rod monochromats
how do they see the world?

Answer 14

-if have cone(your a cone monochromat) the world is in black and white
-if you are a rod monochromat world is also black and white
-the difference is that cone monochromates (cones have higher density ) their visuals are detailed, so see the world in high definition, but just black and white. rod monochromats however, they don’t have good resolution so everything is blurry. rods saturate in bright conditions, so they would have to wear glasses during the day, to reduce light levels for rods to function or they would be totally blind.

Question 15

colour deficiencies are more common in ___

Answer 15

men

Question 16

acquired abnormalities of colour vision
-cerebral achromatopsia/dischromatopsia

Answer 16

• ## a selective loss/deterioration of colour vision associated with the damage to temporal and occipital areas of the ventral pathway (loss of colour vision after an injury)

Question 17

acquired abnormalities of colour vision
-aging and diseases of the eye

Answer 17

-ilness, ageing or trauma can cause colour vision anomalies and defects.
-typically disorders of the retinal vascular system and ageing result in yellow-blue losses (congenital anomalies and defects affect the red-green system)
-however optic nerve lessions, cone degeneration and poisons can cause red-green losses

Question 18

cerebral achromatopsia
-temporal cortex in humans
-lingual and fusiform gyrus

Answer 18

-lingual and fusiform gyrus in our cortex is areas in our brain associated with colour processing but also face processing
-processing of face and colour are very close together in the cortex ,so people who have issues with not recognising faces would have issues with colour vision(but since its localised so either left or right of the brain it only applies to one side of the vision left or right)
cerebral achromatopsia
-if its in both sides then the world reduces in colour
-if someone has a bilateral stroke in the corresponding areas of fusiform and lingual gyrus, the world goes black and white for them

Question 19

testing
pseudoisochromatic plates

Answer 19

-at opticians used to check to see if someone can do a profession
-ishihara plates
-plates have something you need to distinguish (in the photo its a number 6)

Question 20

testing
anomaloscope

Answer 20

• a pattern, a semi circle one side changes colour and one is yellow, you get someone to adjust the changing side to match the colour

Question 21

the farnsworth-munsell 100 hue test

Answer 21

-used in hospitals
-have tiny dials and each one has different colours
-shuffle them and ask person to put them in order
-by plotting errors can see if someone has colour deficiency

Question 22

colour vision through life

Answer 22

children have not great colour vision
teenagers have the best
as you get older colour vision deteriorates