additive colur theory , subtractive theory , munsell ,oswalt law

1. Building Technology (Electrical)
UNIT - IV
BUDHA COLLEGE
OF
ARCHITECTURE
SUBMITTED BY
GAURAV VASHISHTH
 COLOR THEORY
 ADDITIVE COLOR THEORY
 SUBTRACTIVE COLOR
THEORY
 MUNSELL COLOR THEORY
 OSTWALD COLOR THEORY
 SODIUM VAPOR LAMP
 MERCUARY VAPOR LAMP

2. COLOR THEORY
oColor is the byproduct of the spectrum of light, as it is reflected or
absorbed as received by the human eye and processed by the
human brain.
COLOR TERMS
Hue : another name for color
Tint : color + white
Tont : color + gray
Shade : color + black
Value : brightness or darkness of the color
Saturation : the purity of the color.
THERE ARE 12 HUES . ANY OTHER COLOR IS A TINT, TONE OR SHADE
ONE OF THESE HUES , UNLESS IT IS A NATURAL.
COLOR WHEEL
o The color wheel is a visual
representation of color theory:
o According to color theory,
harmonious color combinations use
any two colors opposite to each
other on the color wheel,
 Any three colors equally spaced
around the color wheel forming a
triangle,
A color wheel or color circle is an organization of color hues around
a circle, which shows the relationships between primary
colors, secondary colors, tertiary colors
OR

3. PRIMARY COLORS
• 0˚ = Red
• 120˚ = Green
• 240˚ = Blue
Visual subtractive primaries: Cyan, magenta, yellow (CMY) .
The basic colors that can be
mixed to make all other colors.
The primary colors cannot be
made by combining other
colors.
SECONDARY COLORS
• 60˚ = Yellow
• 180˚ = Cyan
• 300˚ = Magenta
Colors that are made by mixing two
adjacent primary colors
. For example, red and blue light mixed
give magenta light. Mixing secondary
colors: Orange, violet, and green.
Visual additive secondary colors: Cyan, magenta, and yellow
(CMY)
 Visual subtractive secondary colors: Red, green, blue (RGB ) .
Mixing primaries: Red, yellow,
blue (RYB) Visual additive
primaries: Red, green, blue (RGB)
TERTIARY COLOURS
Intermediate, or Tertiary, colors are created by mixing a
primary and a secondary
1. Red- Orange 4. Blue-Green
2. Orange- Yellow 5. Blue-Purple
3. Yellow- Green 6. Red-Purple

4. COMPLEMENTARY COLORS
Complementary colors sit opposite each other on the color wheel.
Because they are opposites, they tend to look especially lively when
used together.
When complementary colors put together, each color looks more
noticeable.
Red and green are an example of complementary colors .
ANALOGOUS COLORS
Analogous colors sit next to each other on the color wheel. They
tend to look pleasant together because they are closely related.
Orange, yellow-orange, and yellow are an example of analogous
colors
NEUTRAL COLORS
Neutral colors don't usually show up on the color wheel. Neutral
colors include black, white, gray, and sometimes brown and beige.
They are sometimes called “earth tones.”
WARM COLORS
Warm colors are made with red, orange, yellow, or some
combination of these. Warm colors tend to make you think of
sunlight and warmth.
COOL COLORS
Cool colors are made with blue, green, purple, or some
combination of these. Cool colors might make you think of cool
and peaceful things, like winter skies and still ponds.

5. TYPES OF COLOUR THEORIES
SUBTRACTIVE THEORY
oThe subtractive, or pigment theory
deals with how white light is absorbed
and reflected off of colored surfaces.
oBlack absorbs most light
oWhite reflects most light
oColored Pigments absorb light and
reflect only the frequency of the pigment
color.
oAll colors other than the pigment colors are absorbed so this is
called subtractive color theory.
oThe primary colors in Subtractive Theory are:
Cyan( C ) Yellow ( Y )
Black( K ) Magenta( M )
oSubtractive or Pigment Theory is used in printing and painting.
ADDITIVE THEORY
o The additive, or light theory
deals with radiated and filtered
light.
oBlack radiates no light
oWhite (sun) radiates all light
oVideo is the process of capturing and
radiating light, therefore it uses Additive
(Light) Theory not Subtractive (Pigment)
Theory.
The primary colors in Additive Theory are:
Red ( R ) Blue( B )
Green( G )
oThe primary colors add together to make white
oLight Theory is also called Additive Theory.
oLight Theory is used in Television, theater lighting, computer
monitor.

6. MUNSELL COLOR THEORY
oThe Munsell Color Order
System is a three-
dimensional model based on
the premise that each color
has three qualities or
attributes: hue, value and
chroma
oMunsell established
numerical scales with
visually uniform steps for
each of these attributes.
oUsing the Munsell nomenclature HV/C, our vivid red example would
have the Munsell notation 5R 6/14. 5R is the hue (red), 6 is the value
(moderately light), and a 14 chroma indicates a highly chromatic
color.
oThe notation for a neutral color is written: NV
oThe chroma of a neutral color is zero, but it is customary to omit
the zero in the notation.
o The notation N 1/ denotes a black, a very dark neutral, while N 9/
denotes a white, a very light neutral. This notation for a middle gray
is N 5/.

7. OSTWALD COLOUR THEORY
oThe Ostwald system creates a color
space based on dominant
wavelength, purity, and luminance,
mapping the values of hue,
saturation and brightness.
oEstablishing the values for these
parameters is done with a disc
colorimeter which mixes on a disk
amounts of the pure spectral color at
the dominant wavelength with
white, and black .
oThus the point in the Ostwald color space is represented by values
C,W, and B to represent the percentages of the circle.
oThe full colors are arranged around a complete circle starts out with
four basic colors: yellow to the north; red to the east; blue to the
south; and sea-green to the west.
oWith these eight colors, Ostwald constructs 24 color-hues with
equal spacing and numbers them from yellow upwards, arranging
them into a circle.

8. SODIUM-VAPOR LAMP
A sodium-vapor lamp is a gas-discharge
lamp that uses sodium in an excited state to
produce light.
There are two varieties of such lamps
Low pressure
High pressure
Low-pressure sodium lamps are highly
efficient electrical light sources, but their
yellow light restricts applications to outdoor
lighting such as street lamps
High-pressure sodium lamps produce a broader spectrum of light
than the low-pressure lamps, but they still have poorer color
rendering than other types of lamps
Low-pressure sodium lamps only give monochromatic yellow light
and so inhibit color vision at night
LOW-PRESSURE SODIUM
oLow-pressure sodium (LPS) lamps have
a borosilicate glass gas discharge tube (arc
tube) containing solid sodium, a small
amount of neon, and argon gas in
a Penning mixture to start the gas
discharge.
oThe discharge tube may be linear or U-
shaped
oWhen the lamp is first started, it emits a dim red/pink light to
warm the sodium metal; within a few minutes as the sodium
metal vaporizes the emission becomes the common bright yellow
oThese lamps produce a virtually monochromatic light averaging a
589.3 nm wavelength .

9. HIGH-PRESSURE SODIUM
oHigh-pressure sodium lamps are
commonly used as plant grow lights.
They have also been widely used for
outdoor area lighting such as streetlights
and security.
oHigh-pressure sodium lamps are quite efficient—about 100 lm/W.
The higher power lamps (600 W) have an efficiency of 150 lm/W.
oBecause the high-pressure sodium arc is extremely chemically
reactive, the arc tube is typically made of translucent aluminum oxide
oXenon at a low pressure is used as a "starter gas" in the HPS lamp. It
has the lowest thermal conductivity and lowest ionization potential of
all the non-radioactive noble gases. As a noble gas, it does not
interfere with the chemical reactions occurring in the operating lamp
THEORY OF OPERATION
oAn amalgam of metallic sodium and mercury lies at the coolest part
of the lamp and provides the sodium and mercury vapor that is
needed to draw an arc.
oThe temperature of the amalgam is determined to a great extent by
lamp power.
The higher the lamp power, the higher will be the amalgam
temperature
The higher the temperature of the amalgam, the higher will be
the mercury and sodium vapor pressures in the lamp and the
higher will be the terminal voltage.

10. oAs the temperature rises, the constant current and increasing
voltage consumes increasing energy until the operating level of
power is reached.
For a given voltage, there are generally three modes of operation:
1. The lamp is extinguished and no current flows.
2. The lamp is operating with liquid amalgam in the tube.
3. The lamp is operating with all amalgam evaporated.
oThe first and last states are stable, because the lamp resistance is
weakly related to the voltage, but the second state is unstable.
oAny anomalous increase in current will cause an increase in power,
causing an increase in amalgam temperature, which will cause a
decrease in resistance, which will cause a further increase in current
oThe light from the lamp consists of atomic emission lines of
mercury and sodium, but is dominated by the sodium D-line
emission. This line is extremely pressure (resonance) broadened and
is also self-reversed because of absorption in the cooler outer layers
of the arc, giving the lamp its improved color
rendering characteristics.
Day time Night time

11. MERCURY VAPOR LAMPS
The mercury vapor lamp is a high intensity discharge lamp. It uses an
arc through vaporized mercury in a high pressure tube to create very
bright light directly from it's own arc.
Advantages:
- Good efficiency (lamps after
1980s have a high lumen per watt
rating)
- Color rendering is better than
that of high pressure sodium
street lights
- Some lamps last far longer than
the 24000 hour mark, sometimes
40 years
Disadvantages:
- Like many lamps it contains
traces of mercury which must be
disposed of properly
- HPS streetlights have a better
lumen per watt rating
- Human skin looks green under
the light, it is poor for color
film/photography
-Warm up time required to start
the lamp
LOW PRESSURE
oThe first mercury vapor lamps were in a
lower pressure tube. One would tip the lamp,
and electrical contacts on each side of the
lamp would send electricity through a liquid
mercury which started the lamp.
oAfter that the lamp would heat fast and
mercury became a vapor. The light would
intensify as the arc grew stronger in the tube.

12. HIGH PRESSURE
oLamps of today are high pressure lamps with a fused quartz
inner discharge tube.
oThis lamp start with a small arc between the starting electrode
and the main electrode. This arc goes through argon gas which
easily strikes, even in cold weather. This little arc heats the tube,
and over several minutes the tube gets hot enough to vaporize
the solid mercury stuck to the sides. The mercury vaporized
creates a strong light between the two main electrodes.
oTo prevent the arc from infinitely getting stronger a ballast
limits the current. Some lamps are "Self Ballasted", they use an
incandescent filament to act as a resistor, limiting current. Home
lighting fixtures usually use the self-ballasted type where as the
more expensive but more efficient ballasted lamps are found in
large fixtures for municipal lighting