COLOR

COLORKEY TOPICSVISIBLE SPECTRUM COLOR VISIONBLACK AND WHITECOLOR ADDITIONCOLOR SUBTRACTIONCOMPLIMENTARY COLORS

COLOR SENSORSCONES SENSITIVE TO COLORTHE PRODUCE THE SENSATION OF COLOR

RODS SENSITIVE TO LIGHTRESPOND TO LIGHT, BUT PRODUCE NO COLOR SENSATION

Color VisionPrimary colorsPerceiving ColorWhat are the primary colors?

Color VisionPrimary colorsPerceiving ColorRed Green Blue

Color VisionPrimary colorsPerceiving ColorWhat makes them primary?

Color VisionPrimary colors

Every color (hue) can be created by blending light of the three primary colors in differing proportionsPerceiving Color

Color VisionPrimary 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 typesPerceiving Color

Color VisionPerceiving ColorFour absorption peaks in retina: 3 cone types plus rodsAbsorption/Cone response

THE PhET SIMULATION CALLED COLOR VISION SHOWS HOW AN OBSERVER CAN PERCEIVE NEW COLORS BY ADDING WAVELENGTHS OF RED, BLUE AND GREEN LIGHT.

Color VisionBlueGreenRedBlueWavelength InputConeSignal to Brain

Color VisionBlueGreenRedGreenWavelength InputConeSignal to Brain

Color VisionBlueGreenRedRedWavelength InputConeSignal to Brain

BlueGreenRedYellowEqual Parts Red and Green =Wavelength InputConeSignal to BrainColor Vision

Color VisionBlueGreenRedYellowEqual Parts Red and Green =Wavelength InputConeSignal to Brain

Color VisionBlueGreenRedYellowEqual Parts Red and Green =Wavelength InputConeSignal to Brain

Color VisionTrichromatic theory of color vision:brain interprets the relative amounts of signaling from each of these cone types

Color VisionTrichromatic theory of color vision:brain interprets the relative amounts of signaling from each of these cone typesThis means that some colors can be matched by a pair of wavelengths

Color VisionTrichromatic theory of color vision:brain interprets the relative amounts of signaling from each of these cone typesThis means that some colors can be matched by a pair of wavelengthsThis also means that any color can be matched by mixing (not more than) three different wavelengths

Color VisionTrichromatic Theory can explain some aspects of colorblindness:most of us are trichromatssomeone missing one of the three cone types is a dichromatsomeone missing two is a monochromatsomeone missing all cone types is called a rod monochromat (very poor vision!)

Color VisionTrichromatic 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 VisionIshihara Color Plates can indicate color blindness

DONT DO THIS !~3% of male readers will have trouble seeing it!

Color VisionBut this is OK.

Color VisionSo is this.

Color VisionEven this is good.

Color VisionWhite light is a mixture of wavelengthsprisms decompose white light into assorted wavelengthsOR recompose a spectrum into white lightWavelength and Color

Additive vs. Subtractive

There are two different ways to mix colors.

Additive vs. Subtractive

What do you get if you use a prism to combine all wavelengths of light?

Additive vs. Subtractive

What do you get if you use a prism to combine all wavelengths of light?

Additive vs. Subtractive

What do you get if you mix a bunch of paint?

Additive vs. Subtractive

What do you get if you mix a bunch of paint?

Additive vs. Subtractive

Additive mixing is most intuitive:ADD wavelengths:

red+green = yellowred+blue = magentablue+green = cyanred+green+blue=white

COLOR ADDITIONTHE ILLUMINATION OF OBJECTS WITH MULTIPLE COLORED LIGHT SOURCES.

ADDITIVE PRIMARIESRED - BLUE GREEN THESE COLORS CAN BE USED TO STIMULATE THE THREE DIFFERENT CONES AND PRODUCE ALL POSSIBLE COLORS.

RULES OF COLOR ADDITIONTHE ADDITIVE PRIMARIES CAN BE USED TO PREDICT THE COLOR OF A WHITE OBJECTRED + BLUE = MAGENTABLUE + GREEN = CYANRED + GREEN = YELLOW RED + GREEN + BLUE = WHITE

APPLICATIONS OF COLOR ADDITIONSTAGE LIGHTINGCOLOR TELEVISION

Subtractive mixing is much less intuitive (but much more common)Subtractive mixing happens when we mix pigments (paint) togetherDifferent pigments subtract different wavelengths:red subtracts all but red, blue all but blue, green subtracts blue and red, etc

Example: blue + yellow = greenTechnically its called cyan

SUBTRACTIVE PRIMARIESTHE SUBTRACTIVE PRIMARIES CAN BE USED TO REMOVE WAVELENGTHS FROM WHITE LIGHT TO PRODUCE ALL OTHER COLORS.

YELLOW CYAN MAGENTA

The result of a mixture depends on what wavelengths dont get absorbed by the two pigmentswavelengthAmount of reflectionbluegreenyellowred

Both yellow and blue pigments reflect a bit of greenwavelengthAmount of reflectionbluegreenyellowred

RULES OF COLOR SUBTRACTIONWHITE YELLOW = BLUE

WHITE CYAN = RED

WHITE MAGNETA = GREEN

COLOR SUBTRACTIONCommon applications:Mixing pigmentsTechnicolor movies

Subtractive mixing is commonly used in color printers

BLACKTHE SENSATION THAT OCCURS AT NO OR LOW LIGHT INTENSITY.

AN OBJECT MAY APPEAR BLACK IF THE INTENSITY OF ITS REFLECTED LIGHT IS MUCH LOWER THAN THE SURROUNDINGS SO THAT IT APPEARS THAT NO LIGHT IS COMING FROM THE OBJECT.

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