from the spectrum lab: light waves with different wavelengths appear as different colors. short...
TRANSCRIPT
From the spectrum lab:• Light waves with different
wavelengths appear as different colors.• Short waves are blue/purple.• Long waves are red.
Missing colors?• Can you find these colors in
the spectrum?
More than just wavelength...• There is no “brown” or “pink”
wavelength of light.• Color is a PERCEPTION, not a
reality. That is:–Color only exists in your mind.
False motion
Scintillating Blocks
Shadow and Color
White’s Illusion
Opponent Afterimage
McCollough Effect
Color opponency
What is going on?• You cannot trust your brain.• Your perception of the world is
different than the actual world.
Other color craziness
• [Greenpro2009 videos: chameleon, color constancy]
• [Himba Tribe study]
Real spectra...• Objects emit/reflect light with
different sets of wavelengths.–Bright in areas, dark in others:
Perfect emitter at 4000 K:
The Sun:
Electrified neon gas
Spectra and the eye• Eyes can’t see all that detail.• Can’t measure the amount of
light of every wavelength.• They check THREE PARTS of
the spectrum...– red, green, and blue parts
Rods and Cones• Four types of light-detecting cell
in your eye:– Rods: very sensitive to all light– Cones: less sensitive, tuned to
certain colors (Red, Green, Blue)
Rods and Cones• Sensitivity of the 3 cone cells:
Primary colors• 3 cones → 3 primary colors• Computers and TVs display
colors with an “RGB” system for Red, Green, and Blue.
RGB Pixels
Color Addition
Primary colors• “Red, yellow, blue” are a BAD
CHOICE for primary colors.• Even in pigments! They can’t
make a full color gamut (range).• Cyan, Magenta, and Yellow form
the CMYK system for pigment/ink.
Color Subtraction
Different numbers of cones• Some humans only have 2 types of
cone! They are color deficient or color blind. (About 1% of men.)• Some women may have 4 cones!!
They’d see differences in color that nobody else does! Tetrachromacy in humans is a new, uncertain discovery.
Colorblindness test
Colorblind simulation:
red-green def. blue-yellow def.
Cones in other animals•Most mammals have 2 types.–Dogs don’t see in black & white!–It’s just a limited set of colors.
• Higher primates have 3 types.• Some birds, reptiles, and insects
have 4 or even 5!
Different cone sensitivity• The cone cells in most birds and
insects can detect ultraviolet!•Many things have “hidden”
features that they can see!