physiology of colour

Question 1

what is subtractive colour mixing

Answer 1

mix two wavelengths together and what you have left when each has subtracted its wavelengths are some remaining medium wavelengths

Question 2

what is additive colour mixing

Answer 2

mix two light together and what you get is the addition of light being reflected off the surface

Question 3

what is the principle of univariance

Answer 3

respinse of a photoreceptor is a function of just one variable (number of photons absorbed)

Question 4

describe weak light and principle of univariance

Answer 4

at wavelength of peak sensitivty (few incidents photons, a large fraction of the of them absorbed)

Question 5

describe strong and the principle of univariance

Answer 5

of lower sensitivuty (many incididence photons a small fraction are absorbed)

Question 6

what does the spectrum graph of absorbed wavelengths show

Answer 6

medium cone gets same activation from blue and orange light

short wavelenght cone activated most for blue lightand not at all for orange light

Question 7

what does the spectrum graph of absorbed wavelengths suggest

Answer 7

to see a different colour you need to compare differences in L M and S cones

Question 8

what were hermann ludwig von helmholts 3 key concepts

Answer 8

you match any visible light with a combo of three spectral lights due to three classes of light detectors
there are infinately many spectra that give rise to same colours= metamers
there seem to be four unique hues

Question 9

what is opponent processinf

Answer 9

there are three cone types

three cones can code three pieces of info about stimulus = coordinated in cone space

Question 10

what is adaptation

Answer 10

neurons adjust firing to adap to average stimulus

Question 11

describe colour adaption in retina

Answer 11

different cones adapt to colour theyre sensing

when neutral background is shown opponent channels are balanced and respond around 0

Question 12

describe humans dimensions

Answer 12

3 dimensions = 3 axes = 6 end points

Question 13

describe relationship between L and M cones

Answer 13

very close so process very similar information and this is inefficient

Question 14

what are L and M cones being similar inefficient

Answer 14

bandwidth out of is expensive- fatter optic disk, thicker nerve fibre layer

Question 15

how do we code L M and S cones differently

Answer 15

use cone responses

Question 16

what are the 3 cdimensions of colour vision

Answer 16

L-M
L+M
S-(l+M)

Question 17

describe L-M dimension of colour vision

Answer 17

also called opponent red/green axis and signals differences in quantal catches of L and M cones

Question 18

describe L+M colour vision

Answer 18

the luminance axis signals the sum of L an M cone catches

Question 19

describe s-(l+m) colour vision

Answer 19

an opponent blue-yellow axis

Question 20

what range is colour visible over

Answer 20

spatial temporal frequencies

Question 21

describe changing luminance and colour vision

Answer 21

edges more visible even for high frequencies

Question 22

what is the general cause of colour blindness

Answer 22

missing or abnormal opsin genes- usually L and M

Question 23

why are L and M cones more involved in colour blindeness

Answer 23

they are on x chromosome and so men are more affectede

Question 24

what is the most common colour deficit

Answer 24

anomalous trichromacy

Question 25

what is anomolous trichromacy

Answer 25

discrimination is poorer along red/green axis but still present

Question 26

what is the rarest colour deficiency

Answer 26

tritanopia where individuals lack functioning s cones

Question 27

what cause colour deficits

Answer 27

faulty opsin genes

Question 28

what does loss of L or M opsins lead to

Answer 28

loss of red/green leaving blue/ yellow

Question 29

what does loss of s opsin lead to

Answer 29

leaves only red/green

Question 30

what is protanopic

Answer 30

lost l opsin

Question 31

what is deuteranopic

Answer 31

lost m opsin

Question 32

what is tritanopic

Answer 32

lost s opsin

Question 33

what is a key component of the ecology of colour vision

Answer 33

many animals only have L and S cones