Colour Vision (4) Flashcards
When visible light falls on an object…
It is either reflected (solid objects)
Or
Transmitted (transparent objects)
What do photoreceptors contain
Photopigments (the light absorbing molecules)
How many types of photo pigment are there in the eye
4 - 1 for rods, 3 for cones
What are the differences in spectral sensitiveness of photoreceptors due to?*
The absorption spectra of the individual visual pigments
Rod and cone pigments absorb best at.. **
Rod - 500 nm
Cone - 419 ; 532 ; 558 - Short, Medium and Long
What is the principle of uni variance
Individual cones are ‘colour blind’
Colour perception is based on how many different types of cones?
3 (trichromatic colour vision) - combinations of the responses across these lead to perception of all colours
Individual cones are colour blind (principle of univariance)
Opponent-process theory of colour vision
4 primary chromatic colours that are processed by 2 perceptually opponent channels
L cones with those of M cones
S cones with those of L+M cones
Monochromats have..
Only rods and no functioning cones
True colour blindness
Protanopia
No L cones
Deuteranopia
No M cones
Tritonopia
No S cones
Can dichromats see colours?**
Yes! Protanopes, Deuteranopes & tritanopes all have 2 (di) pigments and their neural circuits; it is only rod monochromats that will have no colour vision at all
