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Color theory explains what color is

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January 14, 1991

COLOR1.ASC
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Color Theory Basics

Color theory explains what color is, how the human eye sees color
and the methods used to create all the colors in the color spectrum.

To begin learning about color, we must start with light. We must
have light to see things. Light shines on an object and is
reflected back to our eyes, allowing us to see the objects as they
are. Objects ONLY REFLECT THE COLORS THEY ARE MADE UP OF, and it is
these colors that are received by the eye.

When we refer to light, we mean white light. White light is made up
of EQUAL AMOUNTS of RED, GREEN and BLUE light. If we were to shine
three PURE beams of red, green and blue light together and slightly
overlap them, we can see that where the three overlap, the color is
white.

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PRIMARY COLORS

RED, GREEN and BLUE are referred to as the PRIMARY COLORS of light.
Because we ADD them together to create color, we call them ADDITIVE
COLORS.

Where two of the beams overlap, we actually create a third different
color.

Where we overlap the BLUE and GREEN, we create a new color known as
CYAN. CYAN is a combination of blue light and green light.

Where BLUE and RED overlap, we get a color called MAGENTA. MAGENTA
is a combination of blue and red light.

Where the RED and GREEN beams overlap, we create YELLOW! Remember,
these are pure beams of colored light. YELLOW is created by
combining equal amounts of red and green light.

CYAN, MAGENTA and YELLOW are called the SUBTRACTIVE COLORS, because
we create color by using them to SUBTRACT COLOR from WHITE LIGHT.

To help us keep these colors in proper perspective with each other,
we shall refer to the color triangle below. The colors at the

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POINTS of the triangle are the three additive colors, RED, GREEN and
BLUE.

The three colors along along the SIDE of the triangle are the
SUBTRACTIVE COLORS, MAGENTA, YELLOW, and CYAN. The subtractive
colors are placed between the two additives that they are made up
of. For example, the magenta is between the red and blue because
red and blue make magenta.

RED
@
* *
(R + B = M) MAGENTA<<<<@ @>>>>YELLOW (R + G = Y)
* *
* *
BLUE<<<<@ * * * * @ * * * * @>>>>GREEN
CYAN
(B + G = C)

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Up until now, we have been combining two primary colors at a time.
What would happen if we add together one SUBTRACTIVE color and one
ADDITIVE color of light?

Red + Cyan = White Light
(green + blue)

Blue + Yellow = White Light
(red + green)

Green + Magenta = White Light
(red + blue)

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COMPLIMENTARY PAIRS

Complimentary pairs are the combination of one additive and one
subtractive color together to recreate white light.

If you keep in mind that the subtractive colors are made up of two
additive colors, by adding the remaining additive color we get white
light again.

Blue is complementary to Yellow
Green is complementary to Magenta
Red is complementary to Cyan

In most of the situations where we find color, it has been derived
through the subtractive process. Paintings, photographic prints and
color negative film all rely on the SUBTRACTIVE colors to create
color.

The most common application of the additive colors is television.
It uses a combination of red, green and blue dots to create a color
picture on the screen.

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FILTERS

A filter is a device that will block out certain amounts or kinds of
light.

A NEUTRAL FILTER ABSORBS EQUAL AMOUNTS of the red, green and blue
that make up the white light. The transmitted colors, or those
allowed to pass, are the same as the original colors, just not as
intense.

NEUTRAL FILTER

WHITE RED>>>>>>>>>>>>>NNN>>>>>>>>>>RED all
LIGHT RAYS GREEN>>>>>>>>>>>NNN>>>>>>>>>>GREEN colors
BLUE>>>>>>>>>>>>NNN>>>>>>>>>>BLUE pass

Neutral shades of sunglasses produce this effect of reducing the
intensity of the colors without changing the colors themselves.

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In the photographic process, subtractive colors are used to create
color. Color filters are used to SELECTIVELY choose what color we
want to see while eliminating other unwanted colors from light. The
use of filters is basic to the understanding of how photographic
film and paper are designed to reproduced the colors of the subject.

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If a RED filter is placed in front of a beam of white light, you
will see the color RED. Red light is allowed to pass or be
transmitted through while the green and blue light are blocked or
absorbed.

RED FILTER

WHITE RED>>>>>>>>>>>>>RRR>>>>>>>>>>RED only RED
LIGHT RAYS GREEN>>>>>>>>>>>RRR passes through
BLUE>>>>>>>>>>>>RRR

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If a GREEN filter is placed in front of a beam of white light, you
will see the color GREEN. Green light is transmitted through while
the red and blue light is absorbed.

GREEN FILTER

WHITE RED>>>>>>>>>>>>>GGG only GREEN
LIGHT RAYS GREEN>>>>>>>>>>>GGG>>>>>>>>>>GREEN passes through
BLUE>>>>>>>>>>>>GGG

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If a BLUE filter is placed in front of a beam of white light, you
will see the color BLUE. Blue light is transmitted through while
the red and green light are absorbed.

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BLUE FILTER

WHITE RED>>>>>>>>>>>>>BBB only BLUE
LIGHT RAYS GREEN>>>>>>>>>>>BBB passes through
BLUE>>>>>>>>>>>>BBB>>>>>>>>>>BLUE

Remember that ANY filter TRANSMITS ITS OWN COLOR.
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If you place a CYAN filter in front of a beam of white light, you
will find the RED light is ABSORBED while the BLUE and GREEN light
are TRANSMITTED. This is because CYAN is MADE UP of BLUE and GREEN
and a CYAN filter TRANSMITS its own color.

CYAN FILTER
(full strength)
WHITE RED>>>>>>>>>>>>>CCC only GREEN & BLUE
LIGHT RAYS GREEN>>>>>>>>>>>CCC>>>>>>>>>>GREEN passes through
BLUE>>>>>>>>>>>>CCC>>>>>>>>>>BLUE
(absorbs RED)

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If you place a MAGENTA filter in front of a beam of white light, you
will find the GREEN light is ABSORBED while the RED and BLUE light
are TRANSMITTED. This is because MAGENTA is a combination of RED
and BLUE.

MAGENTA FILTER
(full strength)
WHITE RED>>>>>>>>>>>>>MMM>>>>>>>>>>RED only RED & BLUE
LIGHT RAYS GREEN>>>>>>>>>>>MMM passes through
BLUE>>>>>>>>>>>>MMM>>>>>>>>>>BLUE
(absorbs GREEN)

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If you place a YELLOW filter in front of a beam of white light, you
will find the BLUE light is ABSORBED while the RED and GREEN light
are TRANSMITTED. This is because YELLOW is a combination of RED and
GREEN.

YELLOW FILTER
(full strength)
WHITE RED>>>>>>>>>>>>>YYY>>>>>>>>>>RED only RED & GREEN
LIGHT RAYS GREEN>>>>>>>>>>>YYY>>>>>>>>>>GREEN passes through
BLUE>>>>>>>>>>>>YYY
(absorbs BLUE)

Each subtractive filter ABSORBS ONE COLOR of light while
TRANSMITTING the other TWO COLORS.

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Often, it is necessary to use more than one filter at a time to
obtain the desired results of blocking out ALL BUT ONE COLOR. The
following diagrams illustrate how a set of two SUBTRACTIVE filters
work together to filter out ALL BUT ONE COLOR from a beam of white
light.

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MAGENTA CYAN
FILTER FILTER
WHITE RED>>>>>>>MMM>>>>>>>>>CCC only BLUE
LIGHT RAYS GREEN>>>>>MMM CCC passes through
BLUE>>>>>>MMM>>>>>>>>>CCC>>>>>BLUE

If a MAGENTA and CYAN filter are used together, you can see the
MAGENTA filter ABSORBS the GREEN and TRANSMITS the RED and BLUE.

Then the CYAN filter ABSORBS the RED and allows the BLUE to be
TRANSMITTED.

We know from our triangle that CYAN is made from GREEN and BLUE, but
since the GREEN was ABSORBED earlier by the MAGENTA filter, there is
NO GREEN for the CYAN filter to be TRANSMITTED, resulting in only
the remaining BLUE color.

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If CYAN and YELLOW are used together, you can see the CYAN filter
ABSORBS the RED and allows the BLUE and GREEN to be TRANSMITTED.
Then the YELLOW filter absorbs the BLUE and allows the GREEN to be
TRANSMITTED.

From our triangle we see YELLOW is made from RED and GREEN, but
since the RED was ABSORBED earlier by the CYAN filter, there is no
RED for the YELLOW filter to TRANSMIT, resulting in only the
remaining GREEN color.

CYAN YELLOW
FILTER FILTER
WHITE RED>>>>>>>CCC YYY only GREEN
LIGHT RAYS GREEN>>>>>CCC>>>>>>>>>YYY>>>>>GREEN passes through
BLUE>>>>>>CCC>>>>>>>>>YYY

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If you use the MAGENTA and YELLOW filters together, you see the
MAGENTA filter ABSORBS the GREEN and allows the RED and BLUE to be
TRANSMITTED. The YELLOW filter then ABSORBS the BLUE and TRANSMITS
the RED.

From the triangle, we can see that YELLOW is made from RED and
GREEN, but since the MAGENTA filter ABSORBED the GREEN earlier,
there is no GREEN, leaving only the remaining RED color.

MAGENTA YELLOW
FILTER FILTER
WHITE RED>>>>>>>MMM>>>>>>>>>YYY>>>>>RED only RED
LIGHT RAYS GREEN>>>>>MMM YYY passes through
BLUE>>>>>>MMM>>>>>>>>>YYY

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With the YELLOW filter first, we see the BLUE is ABSORBED and
TRANSMITS the RED and GREEN. When the RED and GREEN reach the
MAGENTA filter, the GREEN is ABSORBED and the RED light is
transmitted.

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From the triangle, we know MAGENTA is made from RED and BLUE, but
since the YELLOW filter ABSORBED the BLUE earlier, only the RED
component remained to be transmitted.

YELLOW MAGENTA
FILTER FILTER
WHITE RED>>>>>>>YYY>>>>>>>>>MMM>>>>>RED only RED
LIGHT RAYS GREEN>>>>>YYY>>>>>>>>>MMM passes through
BLUE>>>>>>YYY MMM

As this comparison showed, it really isn’t important in which order
the two filters are used, the single color that remains is ALWAYS
the same. Referring to the color triangle will help keep the color
relationships straight for you.

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Now, what would happen if you put ALL THREE SUBTRACTIVE filters in
front of a light beam?

As you can see, the combination of all THREE FILTERS TOTALLY ABSORBS
ALL of the light and NO COLORS are allowed to pass through. Equal
intensity filters of CYAN, MAGENTA and YELLOW make up what is called
a NEUTRAL FILTER. This means that the color of light seen will be
NEUTRAL or HAVE NO COLOR.

MAGENTA CYAN YELLOW
FILTER FILTER FILTER
WHITE RED>>>>>MMM>>>>>>>CCC YYY NO LIGHT
LIGHT RAYS GREEN>>>MMM CCC YYY passes through
BLUE>>>>MMM>>>>>>>CCC>>>>>YYY

Up to this point, we have been talking about FULL STRENGTH filters.
In other words, a full strength CYAN filter would ABSORB all RED
light and TRANSMIT GREEN and BLUE light.

It is possible to VARY THE INTENSITY of the filter so that SOME
amount of colored light will be ABSORBED. This means that a LOWER
INTENSITY CYAN filter would ABSORB some RED and TRANSMIT some RED
light alown WITH the GREEN and BLUE light.

CYAN FILTER
WHITE RED>>>>>>>>>>>>>CCC> > > > > RED only some RED
LIGHT RAYS GREEN>>>>>>>>>>>CCC>>>>>>>>>>GREEN FULL GREEN
BLUE>>>>>>>>>>>>CCC>>>>>>>>>>BLUE FULL BLUE

If we CHANGE THE INTENSITY OF A NEUTRAL FILTER, we will vary the
intensity of RED, GREEN, and BLUE light TRANSMITTED. Since the
filter is NEUTRAL, the RED, GREEN, and BLUE light will be in EQUAL
AMOUNTS causing the light to APPEAR NEUTRAL in color.

The table below will serve as a reference to the three SUBTRACTIVE
colors that are most commonly used as filters in color film and
paper construction. Always keep in mind the COMPLEMENTARY PAIRS.

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Filter Color Light Transmitted Light Absorbed

CYAN GREEN & BLUE RED
(CYAN)

MAGENTA RED & BLUE GREEN
(MAGENTA)

YELLOW RED & GREEN BLUE
(YELLOW)

It is important to mention here that so far we have been discussing
filters that are ideal, or perfect, meaning they absorbe the
complimentary color completely.

In reality, this is not so. The filters are NOT PERFECT, so a small
amount of the complimentary color does get transmitted, and a small
amount of the other two colors are absorbed. However, it should be
noted that the change in intensity will not create a problem.

One must remember that we are dealing with PURE colors.

Shades of pure and complimentary colors arise from the action of
imperfect filtering. Therefore, color correction/compensation must
ultimately be decided by the viewer.

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A REVIEW

WHITE LIGHT is comprised of EQUAL AMOUNTS OF RED, GREEN and BLUE
light added together. Thus, red, green and blue are called the
PRIMARY COLORS of light.

We can also create color by ABSORBING RED, GREEN or BLUE from white
light using SUBTRACTIVE COLOR filters, CYAN, MAGENTA, and YELLOW.

ANY FILTER TRANSMITS ITS OWN COLOR AND
ABSORBS ITS COMPLIMENTARY COLOR.

CYAN absorbs RED light and allows BLUE and GREEN light to pass.
MAGENTA absorbs GREEN light and allows BLUE and RED light to pass.
YELLOW absorbs BLUE light and allows RED and GREEN to pass.

When two or more filters are used together, it doesn’t matter in
which order they are placed, the result will be the same.

When all three subtractive filters of equal intensity are combined,
the result is a NEUTRAL FILTER.

When placed in front of a beam of white light, the light transmitted
will be NEUTRAL in color and its BRILLIANCE depends on the intensity
of the filter.

Filters are not perfect in design, so a very small amount of the
color of light that should be absorbed actually does pass through
the filter.

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If you have comments or other information relating to such topics
as this paper covers, please upload to KeelyNet or send to the
Vangard Sciences address as listed on the first page.
Thank you for your consideration, interest and support.

Jerry W. Decker………Ron Barker………..Chuck Henderson
Vangard Sciences/KeelyNet

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If we can be of service, you may contact
Jerry at (214) 324-8741 or Ron at (214) 242-9346