Colour Vision Flashcards
(28 cards)
how many cone types
3 - 3 cone opsins
red, green, blue
trichromatic theory
a specific colour is a summation of responses from the three primary photoreceptors types
- responding differenting to the same wavelenght
long wave length sensitive
red cons (peak 570)
medium wave length sensitive
green cones (545)
short wave length sensitive
blue cones (445)
peak sensitivity of rods
500
chromaticity
the colour perceived
what does chromaticiity depend on
wavelenght / hue
background composiition
luminance
colour discrimination
cortical function related to perception / visual processing
dark-adapted peak luminosity
blue-green (500nm)
photopic conditions peak luminostity
yellow green 555nm
purkinje shift
shorter wavelenghts become birhgt as luminance is reduced, i.e. with dark adapatation
hue discrimination
depends on having difference photoreceptors types
2+ or more
the more varitety the more sensitive
colour constancy
colour of an object remains the same despitre the wavelenght of refelcted light under varied conditions
neural processing of colour begins at
the level of the ganglion cells
colour-opponent cells
red-green - detect red/green contrast
blue yellow - ontain summed yellow signal from red and greens cones and contrast it with output from blue cones
fine spectral tuning takes places where
V4
how to test colour vision
ishihara plates
farnsweoth munsell 100 hue
D-15 (milder types)
lanthony new colour test - children
optic nerve disease produces
early red/green defects
acquired macular disease prodeuces
blue/yelllow defects
anaomalous trichromatisim
e.g. deuteranolomy
relative deficiency inta cone population
genes for medium (green) and long (red) are coded
on x chromosome
thf inherited x-linked recessive
genes for shot (blue) are coded
on gene 7
thf AD inheritance
