Color

COLORCOLOR

COLORKEY TOPICS

VISIBLE SPECTRUM

COLOR VISION

“BLACK” AND “WHITE”

COLOR ADDITION

COLOR SUBTRACTION

COMPLIMENTARY COLORS

VIDEO

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

Red Increasing Decreasing

Orange Frequency Wavelength

Yellow

Green

Blue

Indigo

Violet

Remember – Roy G. Biv

VISIBLE SPECTRUM

COLOR SENSORS

• CONES – SENSITIVE TO COLOR– THE PRODUCE THE SENSATION OF

COLOR

• RODS – SENSITIVE TO LIGHT– RESPOND TO LIGHT, BUT PRODUCE NO

COLOR SENSATION

COLOR RESPONSE OF CONES

THRESHOLD OF COLOR

THE INTENSITY OF LIGHT BELOW WHICH NO COLOR IS SEEN.

IT IS A RESULT OF THE FACT THAT RODS (LIGHT SENSORS) ARE MORE SENSITIVE THAN CONES (COLOR SENSORS).

COLOR BLINDNESS

• THE DISTORTION OF COLOR PERCEPTION DUE TO REDUCED RESPONSE OF THE CONES.

• IT IS NORMALLY ASSOCIATED WITH THE REDUCED RESPONSE BY ONE TYPE OF CONE. (USUALLY GREEN CONES IN MALES)

• COLOR VISION TEST (online)

THE COLOR OF AN OBJECT

THIS VIDEO SHOWS THAT THE COLOR AN OBJECT APPEARS DEPENDS NOT ONLY ON THE WAY THAT AN OBJECT REFLECTS COLORS, BUT ALSO ON THE COLOR OF THE LIGHT THAT IS ILLUMINATING THE OBJECT.

THE COLOR OF AN OBJECT

THE COLOR THAT AN OBJECT APPEARS DEPENDS ON

1. THE SELECTIVE REFLECTION OF WAVELENGTHS OF THE OBJECT.

2. THE WAVELENGTHS PRESENT IN THE LIGHT THAT IS ILLUMINATING THE OBJECT

3. THE COLOR RESPONSE OF THE OBSERVER

CLASSIFYING BY COLOR

THE COLOR THAT AN OBSERVER ASSIGNS TO AN OBJECT IS THE COLOR THAT IT APPEARS UNDER WHITE LIGHT.

WHITE LIGHT

• LIGHT THAT IS MADE UP OF ALL VISIBLE WAVE LENGTHS OF EQUAL INTENSITY.

• SLIGHT VARIATION IN THE INTENSITY OF WAVELENGTHS CAN STILL PRODUCE THE SENSATION “WHITE”

THE COLOR WHITE

Any combination of wavelengths that stimulates the red, blue and green sensitive cones equally will produce the sensation “white”.

BLACK

THE ABSENSE OF LIGHT

VIDEO

THIS VIDEO SHOWS THAT AN OBJECT WITH A CHARACTERISTIC COLOR MAY APPEAR BLACK IF IT APPEARS MUCH DARKER THAT ITS SURROUNDINGS.

THE COLOR BLACK• THE SENSATION THAT OCCURS AT NO

OR LOW LIGHT INTENSITY.

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

COLOR ADDITION

THE ILLUMINATION OF OBJECTS WITH MULTIPLE COLORED LIGHT SOURCES.

ADDITIVE PRIMARIES

RED - BLUE – GREEN THESE COLORS CAN BE USED TO

STIMULATE THE THREE DIFFERENT CONES AND PRODUCE ALL POSSIBLE COLORS.

SIMULATION

SURENDRANATH’S CD HAS A SIMULATION OF COLOR ADDITION THAT ALLOWS YOU TO PRODUCE ANY COLOR BY VARYING THE AMOUNT OF RED, BLUE OR GREEN LIGHT PRESENT.

RULES OF COLOR ADDITION

THE 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 ADDITION

• STAGE LIGHTING

• COLOR TELEVISION

COMPLIMENTARY COLORS

TWO COLORS WHICH WHEN ADDED PRODUCE WHITE

RED + CYAN = WHITE

BLUE + YELLOW = WHITE

GREEN + MAGENTA = WHITE

COMPLIMENTARY COLORS

• SURENDRANATH’S SIMULATION OF COLOR ADDITION CAN BE USED TO SHOW COMPLIMENTARY COLORS.

• YOU MUST FIRST ADD TWO ADDITIVE PRIMARIES TO PRODUCE A SUBTRACTIVE PRIMARY.

• WHEN YOU ADD THE THIRD ADDITIVE PRIMARY TO THIS SUBTRACTIVE PRIMARY, YOU WILL SEE THAT THEY ARE COMPLIMENTAY, BECAUSE THEY PRODUCE WHITE.

COLOR FILTERS

The PhET simulation called “Color Vision” shows that color filters are named by the color they pass.

COLOR SUBTRACTION

• THE PRODUCTION OF COLOR BY REMOVING WAVELENGTHS OF LIGHT.

• SELECTIVE REFLECTION IS THE MOST COMMON PROCESS FOR COLOR SUBTRACTION.

• SELECTIVE TRANSMISSION WITH COLOR FILTERS CAN BE USED ALSO.

SIMULATION

SURENDRANATH’S CD HAS A SIMULATION OF COLOR SUBTRACTION THAT ALLOWS YOU TO PRODUCE ANY COLOR BY VARYING THE AMOUNT OF YELLOW, CYAN AND MAGENTA LIGHT THAT IS PRESENT.

VIDEO

• A FLASHLIGHT CAN BE USED TO SHOW COLOR SUBTRACTION WHEN COLOR FILTERS ARE PLACED IN FRONT OF IT BEAM.

• A WHITE PIECE OF PAPER MUST BE PLACED IN FRONT OF THE BEAM TO PRODUCE A REGION OF EQUAL BRIGHTNESS

SUBTRACTIVE PRIMARIES

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

YELLOW CYAN MAGENTA

RULES OF COLOR SUBTRACTION

WHITE – YELLOW = BLUE

WHITE – CYAN = RED

WHITE – MAGNETA = GREEN

COLOR SUBTRACTION

Common applications:

1.Mixing pigments

2.Technicolor movies

AFTER-IMAGE• THE CONTINUED RESPONSE OF

CONES AND RODS AFTER THE LIGHT STIMULUS IS REMOVED.

• THE COLOR OF THE AFTER-IMAGE IS THE COMPLIMENT OF THE STIMULUS.

AFTER IMAGE

SUMMARYVISIBLE SPECTRUM

ROYGBIV

COLOR VISIONCONES AND RODS

“BLACK” AND “WHITE”THESE ARE RELATIVE TERMS

COLOR ADDITIONCOLOR TV, STAGE LIGHTING

COLOR SUBTRACTIONMIXING PIGMENTS, MOVIES IN COLOR

COMPLIMENTARY COLORSAFTER IMAGE