Lecture 4 - Colour Sensation and Perception Flashcards
What is the principle of univariance?
The absorption of light by any photoreceptor causes only one effect (isomerisation) no matter what the wavelength.
What are dichromats?
Individuals who can match all colours with two primary lights.
What are anomalous trichromats?
Individuals who match all colours with three primary lights but in different proportions.
What is protanopia?
No L cones
What is Deuteranopia?
No M cones
What is tritanopia?
No S cones
What is colour opponency?
Colours fall into four groups according to how much red, green, blue or yellow they contain (unique hues).
How are is our perception of colours mediated?
It’s mediated by two perceptual channels and they are fed by three types of cones: one channel compares signals from L with those of M and the other compars signals from the S with those of L+M cones.
Why is colour a percept?
There are NO physical colours in the outside world, only different spectral distributions of lights that are reflected from different objects.
Why is it that we can perceive colours?
Because we have 3 types of cones, whose spectral sensitivities occupy different parts of the visible spectrum.
How is our perception of different colours made possible?
By neural circuits that compare the outputs of the 3 different photoreceptors in two colour-opponent channels: R/G & B/Y.
