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Read article by Land for Thursday Article by Anne Treisman coming up in about two weeks. Color Vision. Perceiving Color. Primary colors. What are the primary colors?. Color Vision. Perceiving Color. Primary colors. Red Green Blue. Color Vision. Perceiving Color. Primary colors.
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Read article by Land for Thursday • Article by Anne Treisman coming up in about two weeks
Color Vision Perceiving Color • Primary colors What are the primary colors?
Color Vision Perceiving Color • Primary colors RedGreenBlue
Color Vision Perceiving Color • Primary colors What makes them primary?
Color Vision Perceiving Color • Primary colors • Every color (hue) can be created by blending light of the three primary colors in differing proportions
Color Vision Perceiving Color • Primary colors • Every color (hue) can be created by blending light of the three primary colors in differing proportions • Led to prediction that there must be three (and only three) distinct color receptor types
Color Vision Perceiving Color • Four absorption peaks in retina: 3 cone types plus rods Absorption/Cone response
Color Vision Theories of Color Vision: Trichromatic Theory Signal to Brain Wavelength Input Cone “Blue” Blue “Green” “Red”
Color Vision Theories of Color Vision: Trichromatic Theory Signal to Brain Wavelength Input Cone “Blue” “Green” Green “Red”
Color Vision Theories of Color Vision: Trichromatic Theory Signal to Brain Wavelength Input Cone “Blue” “Green” “Red” Red
Color Vision Theories of Color Vision: Trichromatic Theory Signal to Brain Wavelength Input Cone “Blue” Equal Parts Red and Green = “Green” Yellow “Red”
Color Vision Theories of Color Vision: Trichromatic Theory Signal to Brain Wavelength Input Cone “Blue” Equal Parts Red and Green = “Green” Yellow “Red”
Color Vision Theories of Color Vision: Trichromatic Theory Signal to Brain Wavelength Input Cone “Blue” Equal Parts Red and Green = “Green” Yellow “Red”
Color Vision Theories of Color Vision: Trichromatic Theory • Trichromatic theory of color vision: • brain interprets the relative amounts of signaling from each of these cone types
Color Vision Theories of Color Vision: Trichromatic Theory • Trichromatic theory of color vision: • brain interprets the relative amounts of signaling from each of these cone types • This means that some colors can be matched by a pair of wavelengths • metamers: colors that have no definite single wavelength (e.g. yellow)
Color Vision Theories of Color Vision: Trichromatic Theory • Trichromatic theory of color vision: • brain interprets the relative amounts of signaling from each of these cone types • This means that some colors can be matched by a pair of wavelengths • metamers: colors that have no definite single wavelength (e.g. yellow) • This also means that any color can be matched by mixing (not more than) three different wavelengths
Color Mixing • use color sliders to adjust R,G,B values
Color Mixing • What color can only exist as a metamer (an additive mixture of wavelengths)? In other words, what color cannot be made with a single wavelength?
Color Mixing • What color can only exist as a metamer (an additive mixture of wavelengths)? In other words, what color cannot be made with a single wavelength? Magenta Think about why!
Color Vision Theories of Color Vision • Trichromatic Theory can explain some aspects of colorblindness: • most of us are trichromats • someone missing one of the three cone types is a dichromat • someone missing two is a monochromat • someone missing all cone types is called a rod monochromat (very poor vision!)
Color Vision Theories of Color Vision • Trichromatic Theory can explain some aspects of colorblindness: • dichromats have only two primaries: any color they can see can be matched with differing proportions of the two wavelengths to which they are sensitive
Color Vision Theories of Color Vision: Trichromatic Theory • Trichromatic Theory can explain some aspects of colorblindness: • dichromats have only two primaries: any color they can see can be matched with differing proportions of the two wavelengths to which they are sensitive • most common is deuteranopia (~3% of men, <1% of women) - missing “green” cones
Color Vision Theories of Color Vision: Trichromatic Theory • Trichromatic Theory can explain some aspects of colorblindness: • dichromats have only two primaries: any color they can see can be matched with differing proportions of the two wavelengths to which they are sensitive • most common is deuteranopia (~3% of men, <1% of women) - missing “green” cones • cannot see color difference between reds and greens - but they can see luminance difference
Color Vision Theories of Color Vision: Trichromatic Theory Ishihara Color Plates can indicate color blindness
Color Vision Theories of Color Vision: Trichromatic Theory DON’T DO THIS ! …~3% of male readers will have trouble seeing it!
Color Vision Theories of Color Vision: Trichromatic Theory But this is OK.
Color Vision Theories of Color Vision: Trichromatic Theory So is this.
Color Vision Theories of Color Vision: Trichromatic Theory Even this is good.
Theories of Color Vision: Trichromatic Theory • Problem with Trichromatic Theory:
Theories of Color Vision: Trichromatic Theory • Problem with Trichromatic Theory: YELLOW
Theories of Color Vision: Trichromatic Theory • Problem with Trichromatic Theory: • most people categorize colors into four primaries: red, yellow, green, and blue • some colors simply cannot be perceived as gradations of each other • redish green !? • blueish yellow !? • It is as if these colors are opposites
Theories of Color Vision: Opponent-Process Theory • Opponent-Process Theory • color is determined by outputs of two different continuously variable channels: • red - green opponent channel • blue - yellow opponent channel
Theories of Color Vision: Opponent-Process Theory • Opponent-Process Theory • Red opposes Green • (Red + Green) opposes Blue • Opponent-Process Theory explains color afterimages
Color Vision Wavelength and Color • White light is a mixture of wavelengths • prisms decompose white light into assorted wavelengths • OR recompose a spectrum into white light
Color Mixing • Additive vs. Subtractive There are two different ways to mix colors.
Color Mixing • Additive vs. Subtractive What do you get if you use a prism to combine all wavelengths of light?
Color Mixing • Additive vs. Subtractive What do you get if you use a prism to combine all wavelengths of light? White
Color Mixing • Additive vs. Subtractive What do you get if you mix a bunch of paint?
Color Mixing • Additive vs. Subtractive What do you get if you mix a bunch of paint? Black
Color Mixing • Additive vs. Subtractive WHY?
Color Mixing • Additive mixing is most intuitive: ADD wavelengths: red+green = yellow red+blue = magenta blue+green = cyan red+green+blue=white
Color Mixing • Subtractive mixing is much less intuitive (but much more common) • Subtractive mixing happens when we mix pigments (paint) together • Different pigments subtract different wavelengths: • red subtracts all but red, blue all but blue, green subtracts blue and red, etc…
Color Mixing • Example: blue + yellow = green Technically it’s called “cyan”
Color Mixing • The result of a mixture depends on what wavelengths don’t get absorbed by the two pigments Amount of reflection green yellow red blue wavelength
Color Mixing • Both yellow and blue pigments reflect a bit of green Amount of reflection green yellow red blue wavelength
Color Mixing • Subtractive mixing is commonly used in color printers
Color is an illusion • Everything you’ve learned so far is wrong.
Color is an illusion • Everything you’ve learned so far is wrong. • Well, not really wrong, just far from complete.
Color is an illusion • What color is this box?
Color is an illusion • What color is this box?