Transcript Color Theory

CM-301/302
COLORS
Theory Session
"They'll sell you thousands of greens. Veronese green and emerald
green and cadmium green and any sort of green you like; but that
particular green, never."
Pablo Picasso, 1966.
A Programme Under the compumitra Series
Copyright 2010 © Sunmitra Education Technologies Limited, India
Outline
About Colours.
Colour Related Terms.
Colour Groups.
Colour Palettes/Models.
About Colours
What is COLOUR
Colour (or spelled as Color) is the property perceived by our
eyes that represents the wavelength of light. It is sensed by
cones and rods (types of cell) in our retina and then
interpreted by our brain.
A non-emissive objects colour means a particular colour
(wavelength) of light that it reflects while all other colours it
absorbs. A black body absorbs all colours in light while a
white body reflects every colour of light. For an emmissive
object obviously a combination colour based on incident light
and emitted light shall be visible.
.
Understanding Colour Perception
Aristotle related colour to light but It was Sir Isaac Newton
who experimentally established this relationship.
Colours are perceived by three different type of cells in our
retina. One can roughly assume it to be equivalent to
perceptors of Red, Blue and Green Colours.
This matches the the concept of 'TRICHROMATIC THEORY'
given by Thomas Young in 1801. This was further endorsed
by James Clerk Maxwell.
The signal that is finally transmitted to our brain is actually
perceived as differential measurement between REDGREEN, BLUE-YELLOW and BLACK-WHITE.
This concept is explained by 'OPPONENT PROCESS
THEORY' given by Helmhotz and Ewald Hering.
Colour sensation in the brain is done by LGN (lateral
geniculate nucleus) in the Thalamus.
Human beings can distinguish about 10 million colours.
Some Interesting Facts About Colours
Almost half the women population have 4
types of colour receptors that make them
sense a large number of colours and effectively
a better colour sense. This is possible due to
presence of two X chromosomes in woman.
4 receptors are available in many species of
spiders, marsupials (kangaroos), birds and
reptiles.
Afterimages made of complementary colours
are often seen after exposure to strong light
beams.
Colour Related Terms
Terms List
Hue
Saturation
Brightness/Lightness
Shade
Tint and Tone
Pigment and Dye
Hue
The colour element is called the hue.
It is the degree to which a particular
colour is explained in terms of basic
colours such as RED, GREEN, YELLOW,
BLUE Etc.
For e.g. Yellowish Red, Greenish Yellow
etc.
Saturation
It is the perceived intensity of a colour.
For e,g. RED, BRIGHT RED, INTENSE
RED.
Practically the lightness also appears to
be increased when saturation is
increased.
Saturation 200%
BRIGHTNESS/LIGHTNESS
It is the perceived
brightness or a shift
towards whiteness of a
particular colour.
SHADE
A colour made darker by adding black
is called its shaded version.
For e.g. sunlight falling on an object
creates a shadow, which often required
shaded colours.
Shades of Blue
Tint and Tone
Mixture of colour with white is called
creating various tints of a colour.
Mixture of colour with grey is called
creating various tints of a colour.
Understanding HSL once again.
In a color sphere ,Colors of the same hue and
saturation, but of different lightness, are said to
be tints and shades. Colors of the same hue and
lightness, but of varying saturation, are called tones
Pigment and Dye
Pigment is a material that is added to
a substance to change the colour of its
reflected light.
Dye is usually the soluble substance to
change the colour of a solution.
Colour Groups
List of Colour Groups
PRIMARY COLOURS
SECONDARY COLOURS
TERTIARY COLOURS
NEUTRAL COLOURS
COMPLEMENTARY and
SUPPLEMENTARY Colours
RAINBOW
PRIMARY COLOURS
It is a set of colours used in a particular
mix to form all other colours.
For emmissive light or CRT the primary
colours are RED, GREEN and BLUE.
These are additive primaries.
For print medium it is CYAN,
MAGENTA, YELLOW and BLACK.
These are subtractive primaries.
For Artists it is RED, YELLOW and
BLUE.
SECONDARY COLOURS
Colours formed by mixing primary colours are called s
secondary colours.
For RGB primaries it would be
Red + Green = Yellow,
Green + Blue = Cyan
Blue + Red = Magenta
For CMY Primaries it would be
Cyan + Magenta = Blue
Magenta + Yellow = Red
Yellow + Cyan = Green
For painters it is
Red + Yellow = Orange
Yellow + Blue = Green
Blue + Red = Violet
Tertiary Colours
Tertiary colours are mix of primary and
secondary colours. For e.g.
Red + Yellow = Orange.
Red + Magenta = Rose.
Neutral Colours
Shades ranging from Black to White
are called neutral colours. These are
popularly called grey shades.
These may have very light mix of other
colours. These are also called low
chroma shades.
Complementary and Supplementary colours
Colours treated as opposite in hue in the same
colour model. For e.g.
in RGB Model
Cyan is complementary of RED.
Yellow is Complementary of BLUE.
In traditional painting.
RED is complementary of GREEN.
Also nearby Tertiary colours on the wheel are
called Supplementary colours. For e.g.
ORANGE is Supplementary to RED.
Usually an aesthetic design is the best
combination of Complementary and
Supplementary Colours.
RAINBOW
Rainbow is a naturally occurring colour group
which is uniformly divided on the basis of
wavelength of light.
It is an excellent aesthetic combination too.
The colour set is :
V – Violet
I – Indigo
B – Blue
G – Green
Y – Yellow
O – Orange
R - Red
COLOUR PALLETES/MODELS
LIST OF PALLETES/MODELS
RGB
CMYK
HSB
UNIFORM
SVG
PANTONE
TRUMATCH
RGB (Red, Green, Blue)
This palette set is meant for images
to be displayed on screen or CRTs.
Maximum number of shades possible
is dependent on system features.
By default 100 preset default shades
are provided in Coreldraw
Application.
For 24 bit colour set 16.7 million
shades are possible.
Value for R, G and B can be
individually set from 0 to 255.
CMYK (Cyan, Magenta, Yellow, Black)
'K' in CMYK comes from Black coloured
Key in CMYK printing system.
This model is meant for traditional as
well as digital printing system as
printing systems are based on
subtractive colours (all colours are
absorbed only required one is
reflected).
HSB (Hue, Saturation, Brightness)
This model allows direct
value based selection of Hue,
Saturation and Brightness
values.
Hue values can be set from
0 to 360 and saturation and
brightness values can be set
from 0 to 100.
SVG
Colour Set Standardised for Scalable
Vector Graphics (SVG) comes under
this model.
This colour set is often used for
Internet based scalable graphics.
Uniform Colors
This set is useful for screen
based drawings where
colours are scattered on
the base of their hue
values.
This set is sometime useful
for easy access of colours
from the palette.
PANTONE
This is a set of colours standardised by
'PANTONE' company.
This set is treated is most standard set
in the colour industry. Even the
national flag, logos etc specify colour
codes from this set.
It provides matching of colours on
various surfaces such as solid uncoated,
solid coated, metallic, matte, metallic
etc.
TRUMATCH
This is large set of palletes for 4 colour
printing that allows easy selection of
colours based on HSB model.
There are 50 hue families shown in the
order of the spectrum, with 40
perfectly proportioned tints and
shades of each hue plus a selection of
4-color greys -- over 2,000 colors in
all. The smooth, precisely proportioned
steps take the guesswork out of 4color selection and matching.
Bibliographical Links
www.wikipedia.org
http://www.colorcube.com/articles/theory/glossary.htm
http://www.colormatters.com/colortheory.html
http://www.worqx.com/color/
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