Chap44

DIGITAL MEDIA FUNDAMENTALS

Explain the terminologies used in describing colours.


In This Chapter, you’ll learn on: Explain the terminologies used in describing

colours: • Hue, Saturation, Value • Luminance • Tints, Tones and Shades Explain what is Additive Colour Explain what is Subtractive Colour


Terminologies Used In Describing Colours Hue Hue is the name of a colour that is red, green, blue

or orange etc, and is often used interchangeably with the word 'colour'. Since there can be many names used to refer to one colour (e.g. some call purple as violet), the 12 hues colour wheel has become a common standard of reference.

Value Value is the range of lightness and darkness within

a hue. Shade and tone are different aspects of value.


Terminologies Used In Describing Colours Saturation This refers to the brightness or dullness of colour,

that is bright red or dull red. Chroma and intensity are synonyms for saturation.

Luminance Luminance refers to a measure to describe the

perceived brightness of a color. You can lighten or darken a color by adjusting its lightness value. Each hue naturally has an individual luminance value. For example, the luminance value of white is 100%. Lighter colours have higher luminance values while darker ones will have lower luminance values.


Terminologies Used In Describing Colours Tints, Tones and Shades A tint is a diluted, pale or delicate variation of a

colour. It is a mixture of a color with white, which increases lightness. A shade of a colour refers to the degree to which a colour is mixed with black, which decreases lightness.A tone is created by adding both white and black to a colour.


Additive Colours

Additive colour theory Additive colour mixing (involved light colours)

is the mixing of projected beams of colored light to form other colours. Additive colour theory had been developed to explain and describe how coloured light is formed.


Additive Colours Looking at the spectrum of visible lights, it is possible to see

that red, green and blue are represented much more strongly than the other colours. Red, green and blue has been recognized that all other colours can be blended from these 3 colours by projecting them on top of each other and white light can be produced again. Thus red, green and blue are termed as Primary colours. (Primary = Original)

G re e n

R e dB lu e

White

Fig 2b – Additive Theory (Red, green and blue lights combined to give white light)


Additive colour mixing Additive colour mixing refers to the mixing of

different colored lights and can be easily demonstrated by the superposition of lights on a white projection screen.

G re e n

R e dB lu e

White

c

M

Y


Additive theory applies to transmitted light and relates to adding red, green, and blue (RGB) together which forms white. The absence of colour is black.

Red (R) + Blue (B) + Green (G) = White

Blue (B) + Red (R) + Green (G) = White

Green (G) + Red (R) + Blue (B) = White


When green and blue light are superimposed, it forms Cyan.

Green (G) + Blue (B) = Cyan (C) When blue and red light are overlapped, it forms

Magenta. Red (R) + Blue (B) = Magenta (M) When green and red light are overlapped, it forms

Yellow. Green (G) + Red (R) = Yellow (Y) This system is called “additive” because all three primaries

“add up” to form white light. Examples where additive colour theory is used are a) Overhead projector


Subtractive colour theory There are two ways of producing a colour, the

additive process and the subtractive one. Subtractive colour theory uses paints, dyes, inks, and natural colorants to create color by absorbing some wavelengths of light and reflecting or transmitting others.

Since white light is made up of red, green and blue

light, the inks subtract out that particular portion or color of light. Whatever light that is left is recognized by the eye as a particular hue.


Subtractive colour theory Cyan ------------- which is white minus red. When

white light (RGB light rays) hits onto an object, red light is absorbed reflecting green and blue light. Green and blue light combines to give cyan.

White light (RGB) – Red (R) = Cyan (C) Magenta -------- which is white minus green, and White light (RGB) – Green (G) = Magenta (M) Yellow ----------- which is white minus blue. White light (RGB) – Blue (B) = Yellow (Y)


Primary Colour

absorbed

Primary Colour

unaffected

Combined colour

achievedRed Blue and Green Cyan

Green Blue and Red Magenta

Blue Red and Green Yellow

Chap44

Business

Transcript of Chap44