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					COLOR
   COLOR
KEY 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.
         VISIBLE SPECTRUM

Red       Increasing    Decreasing
Orange    Frequency     Wavelength
Yellow
Green
Blue
Indigo
Violet
          Remember – Roy G. Biv
       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 OBJECT
RED + BLUE = MAGENTA
BLUE + GREEN = CYAN
RED + 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
      SUMMARY
VISIBLE SPECTRUM
  ROYGBIV
COLOR VISION
  CONES AND RODS
“BLACK” AND “WHITE”
  THESE ARE RELATIVE TERMS
COLOR ADDITION
  COLOR TV, STAGE LIGHTING
COLOR SUBTRACTION
  MIXING PIGMENTS, MOVIES IN COLOR
COMPLIMENTARY COLORS
  AFTER IMAGE

				
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posted:12/18/2012
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