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Trichromacy
- Additive color mixing
- Subtractive color mixing
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Pointilism
- The use of primary color dots to generate other colors
- Printers
- Old t.v.'s
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Additive color mixing deals primarily with;
shining two lights together
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Subtractive Color mixing primarily deals with;
- mixing paints
- photography
- printing for dye
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Subtractive color mixing - Blue + Green=
- White light
- Wave lengths are subtracted; only some shine through
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Yerllow =
medium wavelength
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Color Space
a 3-d space that describes all colors (paint swatches)
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Three dimensions of color
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Hue
Our perception of color; related to the wavelength present
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Saturation
Amount of particular wavelength present; how pure the color is
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Brightness
How intense the color is
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Psychological Dimensions -> Physical Dimensions:
Hue ->
Brightness ->
Saturation ->
- Hue -- Wave length
- Brightness -- Intensity
- Saturation -- Purity
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Opponent Processes
Color processing in the LGN
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Three types of opponent processing
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After Images
A visual image seen after a stimulus has been removed
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Positive after image
image has same colors as object
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Negative after images
image has reversed or complementary colors
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Complementary colors
- 2 colors that when mixed together make gray/white
- Colors that are directly across from each other on color circle
- Spontaneous firing has to balance out/cancel out when looking at blank screen
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Supersaturated after images
small blue square - big yellow rectangle = see blue box in middle
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Does everyone see color the same way?
yes-
- General agreement on colors
- Some variation due to age (lens turns yellow)
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Does everyone see color the same way?
-No
- About 8% of male population are color blind
- 0.5% of women population have some sort of color deficiency
- Color deficits are more common in men because genes coding for retinal cones are located on X chromosome
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Disorders of color perception
- Anomolous trichromatism
- Dichromatism
- Rod monochromat
- Cone monochromat
- Cerebral achromatopsid (damage to cerebrum)
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Normal human color vision is called-
trichromatic
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Anomolous Trichromatism
- People have three cones, they just have fewer of one type of photopigment than they should
- Most common type of color blindness
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Protoanomoly
Have less red cone pigment
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Deuteranomally
Have less green cone pigment
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Tritanomy
Have less blue pigment
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Dichromatism
- Have only 2 types of cones
- Deuteranopia
- Protoanopia
- Tritanopia
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Deuteranopia
lack green cone pigment (missing the whole set of cones, not just a weakness)
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Protoanopia
lack red cone pigment
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Tritanopia
- lack blue cone pigment (looks most distorted)
- spectrum goes from green to red
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Rod monocromat
- no cones only rods
- cant see in the dark
- only see black and white
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Cortical Color Blindness =
- Cerebral achromatopsia
- Problems with cells coding color in cortex
- Cones in retina are fine
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Unilateral Achromatopsia
- Blindness in one side
- 1/2 color, 1/2 black and white (V4)
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Does everyone see color the same way?
-Maybe
- Various cultures describe color differently
- *Quality of overhead light has a lot to do with how we see color
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Color Constancy
- Daylight/Florescent light
- The color of an object stays constant despite changes in the wavelength of light illuminating it.
- Strange because the object is reflecting different wavelengths. But we dont perceive a change in color
- To acheive color constancy, our visual system takes into account the background illuminations
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Memory color
Familiarity and past experience affect our perception ofcolor
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Memory Color Experiment
illuminate green felt objects with red lights
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Many birds have ________ systems; pidgeons have ______
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Bees and butterflies have;
ultraviolet color system
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Manti shrimp have at least ____ different types of cones
12
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Other mammels (dogs, horses, etc) have only ____ cones.
2
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Cats are best categorized as;
anomolous trichromatis
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Binocular depth cue
depth cue that relies on info from both eyes
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Nonmetrical depth
depth cue that provides information about relative depth
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Occlusion
Cue to relative depth in which one object distracts the view of part of another object
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