Examples of Addition and Subtraction of Light

Examples of Addition and Subtraction of Light

1. Computer monitors and television

           

Computer monitors and televisions are the most common examples of additive color. Examination with a sufficiently powerful magnifying lens will reveal that each pixel in CRT, LCD and most other types of color video displays is composed of red, green and blue sub-pixels, the light from which combines in various proportions to produce all the other colors as well as white and shades of gray. The colored sub-pixels do not overlap on the screen, but when viewed from a normal distance they overlap and blend on the eye's retina, producing the same result as external superimposition.

2.    Coloured lights on stage

     The principle of the addition of light is used to produce the attractive lightning effect in concert shows

3.    Photography

     The principle of the subtraction of light is applied in photography or videography to produce a specific visual effect.

Video

Differences between the addition of light and the subtraction of light

The addition of light	The subtraction of light
The mixing of coloured lights to form other colours.	The absorption of specific colours from white light.
The primary coloured lights combine to form secondary coloured lights.	The primary colour filter absorbs all colours except its own colours.
All the secondary coloured lights combine to form white light.	The secondary colour filter absorbs all colours, except its own colour and the colour which forms it.

The Principle of Light Subtraction

The Principle of Light Subtraction

The colour of opaque objects depends on the colour of the light reflected into our eyes.

• Objects with primary colours ( red, blue or green ) will only reflect the light which has the same colour as them.

A red object only reflects red light.

Other coloured lights will be absorbed.

Therefore, the object appears red.

• Objects with secondary colours ( yellow, magenta or cyan ) reflect the light of the same colour and also the light of primary colours which from the secondary colour.

• White objects appear white in white light because the white objects reflect all colours in white light.

White objects reflect all colours in white light.

All coloured lights overlap to produce white colour again.

• Black objects appear black because they absorb all colours in white light.

Black objects absorb all colours in white light.

No coloured lights are reflected.

Therefore, the objects appear black.

Subtraction of lights

Subtraction of light

Subtraction of light occurs when opaque object reflects the light of some colours and absorbs the light of other colours.

Addition of light

Addition of light is the mixing of primary colour lights to produce secondary colour lights

Primary colour	Primary Colour	= Secondary Colour
Red	Blue	Magenta
Green	Red	Yellow
Blue	Green	Cyan
	Red + Blue + Green = White

On this page we've discussed adding red, green and blue light in equal intensities. What happens if they are added in unequal intensities? For instance, suppose you are on the stage lighting team for your school's theatre. Your task is to control the red, green and blue stage lights to produce various color effects for the upcoming show. Use the Color Addition widget below to adjust the strength of the red, green and blue lights relative to full strength. A 1.00 indcates that the light is on at full strength; a 0.00 means the light is off. (All numbers should range from 0.00 to 1.00.) Once adjusted, click the Mix 'Em Up button to find out the result of mixing red, green, and blue components at various strengths

Introduction

Colors are different wavelengths present in white light. When one of the wavelengths is dominant, we observe light with color, because our eyes cannot distinguish the colors when they have large differences of intensity. If the intensity of a light beam is very high for red and very small for the other colors, we see only red.  White light is formed from a combination, with equal intensity, of all waves of the visible spectrum.

The primary colors are those from which all colors are formed. This is because their intensities are higher in different parts of the visible spectrum, so by taking a combination of them and varying their power, new colors appear. The primary colors are red, green and blue.

When mixed, the phenomenon is described as addition of colors. If instead of taking red, blue and green, we join cyan, magenta and yellow (resulting from the mixture of the three above) the result is the primary colors plus black. This is called subtraction of colors.