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Additive Colour Mixingusing a Computer Monitor

You will use: • a Liquid Crystal Display (LCD) or Cathode

Ray Tube (CRT) Computer Monitor, • this PowerPoint slideshow • an eyepiece (12.5x or 15x magnification)• Answer Sheet

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* Answer the Questions on the Sheet Provided. *

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If you can see the numbers below,then this Activity is for you.

(Do you know what kind of test this is?)

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Here’s How the Eye Works.

Rods and cones are special cells in your eye that process light.

Rods help us see black and white and shades of grey. Cones help us see color.

You have 3 kinds of cones – they process red, green, and blue.

Reference: www.howard.k12.md.us/res/eyes/howeyeswork.html

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This is the Colours Application that allows

you to adjust the colour of fonts in Microsoft

a. The colors chart is for your eye’s: rods / cones

(circle one)

b. The contrast slider is for your eye’s: rods / cones (circle one)

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This is how an older CRT monitor makes colours.(For the LCD monitors, it’s a little different…)

Three electron gunsfire electrons (from 2)as electron beams (3), to hit the inside of thecomputer screen (6).When they hit the screen,they cause someof the phosphorus dots to become bright(or illuminated)

The screencontains 3 typesof phosphorus dots:Red, Green and Blue. Each dot colour is foreach type of Conein your Eye!

Reference: http://computershopper.com/feature/how-it-works-crt-monitor

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• The three electron beams illuminate a trio of phosphorus dots called a triad.

• the smallest image you can see is made up of one or more triads and is called a pixel.

Reference: http://computershopper.com/feature/how-it-works-crt-monitor

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• On a LCD monitor, there aren’t dots,

but rather a grid of Red, Green and Blue rows, with black bars separating the rows

http://www.tweakguides.com/Graphics_6.html

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Move your eyepiece toward the screen, up very close to it,

to see the colours in the black circle.

The coloured bars are there in the black circle… but they are not illuminated- they are turned off to make black.

This is black- black occurs when no light is reaching your eye.

(White occurs when all three colours (RGB) hit your eye.)

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Place the eye piece close up tothe red circle

Qa: What colour of bar do you see illuminated inside the red circle?

Qb: Are there any “ingredient” colours of red, or does red “just contain red”?

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Place the eye piece up to thegreen circle

Qa: What colour of bar do you see illuminated inside the green circle?

Qb: Are there any “ingredient” colours of green, or does green “just contain green”?

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Place the eye piece up to theblue circle

Qa: What colour of bar do you see illuminated inside the blue circle?

Qb: Are there any “ingredient” colours of blue, or does blue “just contain blue”?

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Place the eye piece up to thewhite circle

Qa: What colour(s) of bar do you see illuminated inside the white circle?

Qb: Are there any “ingredient” colours of white, or does white “just contain white”?

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BLACK IS NOT A COLOUR

WHITE IS NOT A COLOUR

Black and White depend on the amount of RGB light hitting your Rods and Cones.

(All 3 in equal amounts for White, and none whatsoever for Black)

Q: Why are we saying this about black and white?

If they are not colours, what are they?

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Complete the Colour Equation

+ =

G

+

Check it using your eyepiece!

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Red Green and Blue are called the

Primary Additive Colours.

Primary colours are the basic colours with no ingredients other

than their own.

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This is a Colour Wheel for Additive Colour Mixing

(more on this later)

Note how the colours overlap to produce other colours.

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Place the eyepiece up to the Cyan circle

What “ingredient colours” do you see inside the cyan circle?Answer this by Completing the Colour Equation below:

+ = C

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Place the eyepiece up to the Magenta circle

What “ingredient colours” do you see inside the magenta circle?Answer this by Completing the Colour Equation below:

+ = M

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Place the eyepiece up to the Yellow circle

What “ingredient colours” do you see inside the yellow circle?Answer this by Completing the Colour Equation below:

+ = Y

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Cyan Magenta and Yellow are called the

Secondary Additive Colours.

Secondary colours are made by mixing two primary colors.

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TRAFFIC LIGHTSand your EYES

Examine this white circle with the eyepiece. a: Which two colours of the 3 colours are easiest to see?

Examine each traffic light with the eyepiece.

b: Why do you think we have no blue traffic lights?

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a. What are the colours of Rectangle 1?

b. What are the colours of Rectangle 2?

c. Using your eyepiece, compare the two rectangles. What phosphorus dot is not illuminated in both rectangles?

d. What is the difference between Orange and Brown- are the differences in the colour, or in the shade?

Rectangle 1

Rectangle 2

Comparing Shades of Colours

These two rectangles are actually the same colour- but with different shades.

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What colour are you thinking ofright now?

Please Hand in your Answer Sheet.

The End!