A Programme Under the compumitra SeriesCopyright 2010 © Sunmitra Education Technologies Limited, India

"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.

CM-301/302COLORS Theory Session

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 RED-GREEN, 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

HueSaturationBrightness/LightnessShadeTint and TonePigment 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 COLOURSSECONDARY COLOURSTERTIARY COLOURSNEUTRAL COLOURSCOMPLEMENTARY and SUPPLEMENTARY ColoursRAINBOW

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 ssecondary colours.

For RGB primaries it would beRed + Green = Yellow, Green + Blue = CyanBlue + Red = Magenta

For CMY Primaries it would beCyan + Magenta = BlueMagenta + Yellow = RedYellow + Cyan = Green

For painters it isRed + Yellow = OrangeYellow + Blue = GreenBlue + 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 – VioletI – IndigoB – BlueG – GreenY – YellowO – OrangeR - Red

COLOUR PALLETES/MODELS

LIST OF PALLETES/MODELS

RGBCMYKHSBUNIFORMSVGPANTONETRUMATCH

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 4-color selection and matching.

Bibliographical Links

www.wikipedia.orghttp://www.colorcube.com/articles/theory/glossary.htm http://www.colormatters.com/colortheory.html http://www.worqx.com/color/

Ask and guide me at sunmitraeducation@gmail.com Share this information with as many people as possible.Keep visiting www.sunmitra.com for programme updates.