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!