colour perception Flashcards
Is light a physical property of psychophysical property?
psychophysical
what part of the electromagnetic spectrum do we see?
400 and 700 nm
what are the three basic principles of colour perception?
detection, discrimination and appearance
what is detection for colour perception?
wavelengths of light must be detected
what is discrimination for colour perception?
able to tell the difference between one wavelength and another
what is appearance for colour perception?
want to assign colour to lights and surfaces and have those be stable over time
what is phototopic detection?
light intensities that are bright enough to stimulate the cone receptors and bright enough to saturate rods
what is scotopic detection?
light intensities that are bright enough to stimulate the rod receptors but to dim for cone
what are the 3 types of cone photoreceptors?
s-cones
m cones
l cones
what is the problem of univariance?
an infinite set of different wavelength-intensity combinations can elicit exactly the same response from a single photoreceptor
how are rods impacted by univariance?
they contain the same photopigment molecule and have the same sensitivity
what is the molecule in rods?
rhodopsin
under scoptopic conditions what are active?
only rods
under photopic conditions what is active?
all three cone types
what is trichomacy?
the theory that the colour of any light is defined in our visual system by the relationships of three numbers, the outputs of three receptor types now known to be the cones
what is the trichomatic theory also known as?
the Young-Helmhotz theory
what are metamers?
different mixtures of wavelengths that look identical
what cells are in the lateral geniculate nucleus?
cells that are maximally stimulated by spots of light and receptive fields
what is a cone opponent cell?
a neuron whose output is based on a difference between sets of cones
what is the colour space?
a 3D space that describes all colours
what is the RGB colour space?
defined by the outputs of long, medium and short wavelength lights
what is the HSB colour space?
defined by hue, saturation and brightness
what is opponent colour theory?
the theory that perception of colour is based on the output of three mechanisms; each of them based on an opponency between two colours
what are LGN cells excited by?
l cone onset in centre, inhibited by m cone onsets in their surround
what are other cells excited by?
s cone onset in centre, inhibited by l and m in their surround
what is an afterimage?
a visual image seen after a stimulus has been removed
what is a negative afterimage?
an afterimage whose polarity is the opposite of the original stimulus
what are the types of colourblindess?
deuteranope - m cones
protanope - l cones
tritanope - s cones
what is colour anomalous colour blind?
have two types of cones which are so similar they can discriminate
what is cone monochromat?
only one cone type
what is rod monochromat?
no cones of any type
what is colour contrast?
a colour perception effect in which the colour of one region induces the opponent colour in a neighbouring region
what is colour assimilation?
a colour perception effect in which two colours bleed into eachother, each taking on some of the chromatic quality of the other
what is colour constancy?
the tendency of a surface to appear the same colour under a fairly wide range of illuminants
how do we achieve colour constancy?
must discount the illuminant and determine what the true colour of a surface is
what is an illuminant?
the light that illuminates a surface
