Vision Flashcards
What is the visible light wavelength spectrum?
390nm - 750nm
Rods detect intensity, not wavelength. T/F?
True.
Humans are trivariants. T/F?
True.
S-cones peak at which wavelength?
440nm
M-cones peak at which wavelength?
545nm
L-cones peak at which wavelength?
565nm
Which two colours are easily confused?
Red and green as they overlap a lot on the spectrum. Blue cones are more isolated so easier to distinguish.
What is the Munsell Colour System?
Hue: wavelength
Value: reflectance and luminosity
Chroma: saturation of signal
What is the opponent colour theory?
3 channel theory. They are:
red-green
blue-yellow
black-white
What is the stage theory?
The modern model of normal colour vision which incorporates both the trichromatic theory and opponent colour theory into two stages.
- Receptor stage: 3 pigments
- Neural processing: colour opponency. Post-receptoral.
What is a trichromat?
Person with normal colour vision
What is a dichromat?
colour blindness. sex linked:
Protanopia: less sensitive to red.
Deuteranopia: less sensitive to green.
What is the Ishihara test?
Test with number embedded in dots. Can you see it????
What properties allow colour to be perceived?
Intensity and wavelength.
In the CIE diagram, what is in the centre of the graph?
White Achromatic Point.
Do rods have high light threshold?
No.
Of red, green and blue, which to cone types overlap a lot?
red and green.
What 3 properties are need to fully specify a colour?
Hue (wavelength), value (lightness and reflectance) and chroma (saturation).
What is the trichromatic theory?
A theory based on colour mixing, suggesting a combo of 3 channels explain colour discrimination functions.
What is the opponent colour theory?
Suggests there are 3 channels: red-green, blue-yellow and black-white (responding in an antagonist way).
What is the colour vision pathway at the level of the RETINA for red-green?
L and M cones -> midget ganglion cells -> parvocellular neurons (LGN).
NB: L or M will be stimulated more than the other.
What is the colour vision pathway at the level of the RETINA for blue-yellow?
Blue: S cones -> small bistratified ganglion cells -> koniocellular neurons (LGN).
Yellow: L and M cones together inhibit S cones being stimulated -> small bistratified ganglion cells -> koniocellular neurons (LGN).
