Task 3: Colour Flashcards
“Pure/unique” colors
red, yellow, green, blue - all colors can be described with these
Desaturation
changing color by making light brighter by adding white e.g. red + white = pink
Name the 3 Types of Cone Pigments
S - 419 max - blue
M - 531 max - green
L - 558 max - red
Chromatic colors/hues
(e.g. blue, green, red) occur when some wavelengths are reflected more than others through a process called selective reflection
Selective reflection
objects selectively reflect some wavelength (opaque objects) -> chromatic colours more
Selective transmission
only some wavelengths pass through the object/substance (transparent objects) e.g. cranberry juice
Transmission curves
plots of the percentage of light transmitted vs wavelength
Additive color mixing
mixing lights involves adding up the wavelengths of each light in the mixture
Subtractive color mixture
mixing paints causes fewer wavelengths to be reflected because each paint subtracts wavelengths from mixture
How is black created in relation to subtractive colour mixing
when reflected wavelengths of 2 colors differ, however is rare
Trichromatic theory of colour vision
colour vision depends on the activity of 3 different receptor mechanisms, based on the psychophysical procedure called colour matching
Colour matching experiements
observers adjusted the amounts of 3 different wavelengths of light mixed together in a “comparison field” until the colour matched the colour of a single wavelength in a “test field”
Young-Helmholtz Theory of Color Vision
colour vision depends on 3 receptor mechanisms, each with different spectral sensitivities
- > Light of a particular wavelength stimulates each receptor mechanism to different degrees and the pattern of activity in the 3 mechanisms results in colour perception
- > Therefore, each wavelength is represented in the NS by its own pattern of activity in the 3 receptor mechanisms
How is white formed by receptors?
equal signalling of all 3 receptors
How are cones responsible for 3 different absorption spectra?
the long opsin part of the visual pigments differ
Metamerism
when 2 physically different stimuli are perceptually identical e.g. lights in the trichromatic experiment being physically different but perceptually identical
Metamers
2 identical fields (lights) being perceptually identical but not physically the same, this is due to them resulting in the same pattern of response in 3 cone receptors (2 lights are physically different but when combined look the same)
Isomerization
visual pigment isomerizes (retinal changes shape) when the molecule absorbs one photon of light, this activates the molecule and triggers the process that activates the visual receptor to see light
Color deficiency
partial loss of colour perception, usually due to problems with retinal receptors present at birth
How can color deficiency be determined?
o Colour tests e.g. Ishihara plate
o Using the colour-matching procedure (to determine the minimum number of wavelengths needed to match any other wavelength in the spectrum)
Unilateral dichromat
trichromatic vision in one eye, dichromatic vision in the other (can determine for use what a dichromat sees)
Monochromat
a) how many pigments
b) describe wavelengths
c) visual acuity level
d) colors seen
a) 1 pigment
b) can match any wavelength in the spectrum by adjusting the intensity of any other wavelength therefore needs only one wavelength to match any colour in the spectrum
c) poor, rod system overloaded in strong illumination, sensitive to bright lights
d) white, grey, black
Dichromat
a) how many pigments
b) describe wavelengths
c) name 3 types
a) 2
b) only needs 2 wavelengths to match all other wavelengths in the spectrum
c) protanopia, deuteranopia, tritanopia
Protanopia
is missing the long-wavelength pigment
