Chapter 9: Percieving color Flashcards
cerebral achromatopsia
color blindness caused by a cortical injury
chromatic colors
such as blue, green, and red, occur when some wavelengths are reflected more than others
selective reflection
when some wavelengths are reflected more than others
reflectance curves
plot the percentage of light reflected from objects at each wavelength in the visible spectrum
achromatic colors
such as white, gray and black occur when light is reflected equally across the spectrum
selective transmission
only some wavelengths pass through the object or substance (ex. cranberry juice selectively transmits long wl light (red) and limade selective transmits mid wl light (green))
transmission curves
the plots of the percentage of light transmitted at each wavelength
subtractive color mixture
when you mix colors (like paints) and it subtracts all the wavelengths except some that are associated with the final color -> less wavelengths are reflected
additive color mixture
like mixing lights, this happens when it involves adding up the wavelengths of each light in the mixture rather than subtracting (paints) -> more wavelengths are reflected
saturation
the amount of white that has been added to a particular hue, saturation decreases as more white is added
desaturated
when colors are desaturated they take on a faded or washed-out appearance
hues
another term for chromatic colors
value
refers to the light to dark dimension of color (light red vs dark red, adding of black)
color solid
arranging colors systematically in a 3 dimensional solid
HSV color solid
color solid with the three dimensions of hue, saturation, and color
trichromatic theory of vision
states that color vision depends on the activity of three different receptior mechanisms.
young-hemholtz theory
research that expanded upon the trichromatic theory with color matching experiments
color matching
the experimenter provides a reference color, and thene the subject matches the color by missing different wavelengths of light in a comparison field. found tht participants needed at least 3 colors to make a new color
metamerism
when two physically different stimuli are perceptually identical
metamers
ex. the to identitcal fields in a color matching experiment, they aren’t completely identical but they are percived as identical
principle of univariance
states that once a photon of light is absorbed by a visual pigment molecule, the identity of the light’s wavelength is lost.
monochromats
people who see with just one pigment, so they see in shades of gray
dichromats
people who 2 cone pigments, they see colors but cant distinguish some colors that trichromats can
trichromats
people with 3 visual pigments
opponent process theory
proposed by hering, color wisionis caused by opposing physiological responses generated by bkue and yellow, red and green, and black and white.
color circle
arranges perceptually similar colors next to each other around its perimeter, only concerned with hue
hering’s primary colors
red, yellow, green, or blue
complementary afterimages
each afterimage is the color on the opposite side of the color circle
hue cancellation
using the opposite color to cancel out the color (ex adding more and more yellow light to cancel out the blueness of the original color)
single-opponent neurons
increases firing to medium wavelength presented to the enter of the receptive field and decreass firing to long wavelengths presented to the surround
double-opponent neurons
receptive fields similar to simple cortical cells, usegul for percieving boundaries betwee different colors
monochromatism
rare form of color blindness that is mainly hereditary and occurs in about only 10 peope out of 1 million, they only see in shades of lightness (black, grey, white)
color blind
another word for monochromats, as compared to dichromats who are color deficient
dichromatism
missing one of the 3 cone pigments, which means that they can experience color but not as many colors are trichromats can
ishihara plates
color blind plates with the numbers in the middle
unilateral dichromat
a person with trichromatic vision in one eye and dichromatic vision in the other
protanopia
missing the long wavelength pigment,
deuteranopia
missinf the medium wavelength pigment
tritanopia
missing the short waelength
anomalous trichromatism
mixes the wavelengths in different proportions from a trichromat and is not as good as discriminating between wavelengths that are close together
color constancy
we percieve colors to be relatiely constant even under changing illumination
chromatic adaptation
color perception cna be changed by prolonged exposure to chromatic color. ex. when you stare at a red swuare too long and then look away, things look green
parital color constancy
the perception of the object is shifted after adaptation, but not as much as when there was no adaptation.
memory color
if we know that an objects specific color, we percieve it as more saturated than objects with the same wavelengths , ex a stop sign
lightness
the perception of the shade of achromatic color
lightness constancy
the fact that we see white, blacks and grays as staying about the same shade under different illuminations
ratio principle
as long as the ratio between the reflectance of the bject to the reflectnce of surrounding objects then the percieved lightness will stay the same
reflectance edge
an edge where the reflectance of two surfaces changes
illumination edge
an edge where the lighting changes
penumbra
the fuzzy border at the end of a shadow
spectral colors
colors in the visible spectrum (red orange yellow, green , blue, violet, (sometimes indigo))
non spectral colors
colors that do not appear in the spectrum, but they are a mixture of different colors like magenta (mix of blue and red)
