Colour Vision & Depth Perception Flashcards
(67 cards)
What are the three steps to colour perception?
detection, discrimination, appearence
What is involved in the detection step of colour vision?
detecting wavelengths, need photoreceptors to convert light into signals in nervous system
What is involved in the discrimination step of colour vision?
neurons that compare input from different photoreceptors, how we tell difference between wavelengths
What is involved in the appearence step of colour vision?
how wea assign perceived colours to surfaces
What wavelength do short-wavelength cones peak at?
420 nm
What wavelength do medium-wavelength cones peak at?
535 nm
What wavelength do long-wavelength cones peak at?
565 nm
What wavelenghts do rods peak at?
~500nm
What does the graph of a photoreceptors response to wavelengths look like?
roughly an arc shape with a peak in the middle, x axis is wavelengths, y axis is the response
What is the principle of univariance?
that an infinite set of combinations of different wavelenghts/intensities can cause the exact same response from a single photoreceptor
What explains the lack of colour in dimly lit scenes?
univariance
What is the solution to problem of univariance?
trichromatic solution
How does the trichromatic solution solve univariance?
using all 3 types of cones we can get a unique response for the entire range of visibile light
Explain why humans having three cones allows us to see colour at different intensities?
specific light produces a set of three responses by the 3 cones, so when intensity is changed the response size will change but the relationship between the three responses will not
What are metamers?
different mixtures of wavelengths that look identical
Does mixing wavelenghts change the physical wavelengths?
no, the mixture is only perceived
What is a additive colour mixture?
mixture of lights, all the lights are reflected off the surface to the eye, perception is the effects of the lights added together
What is a subtractive colour mixture?
if pigments A and B mix, some of the light reflected will be subtracted by A and some by B, only the remainder will affect perception
What is the neural basis of discrimination of colours?
compute the differences between cone responses
ex. L - M and (L + M) - S
What does our brain convert the three cone signals to?
L - M, (L + M) - S, L + M
What are cone opponent cells?
found in retina, LGN, and visual cortex, they subtract one cone input from another
What are some examples of cone opponent cells?
L - M, M - L, (M + L) - S, S - (L + M)
What does equilumient mean?
stimuli that vary in colour but not luminence
What is the smallest number of correctly chosen lights that can create all possible colours that humans can see?
Three
