Color TheoryColor Theory

Which colours is white light made of?

Color Mixing Color Mixing

Color can be perceived either from Color can be perceived either from

1) a luminous object (TV, monitor, 1) a luminous object (TV, monitor, projector) using the projector) using the Additive Additive ApproachApproach

2) reflected pigment or ink 2) reflected pigment or ink (printouts, materials) using the (printouts, materials) using the Subtractive ApproachSubtractive Approach

Additive Color ModelAdditive Color Model Used by luminous objects Used by luminous objects

ex. Computers, TV, projectorsex. Computers, TV, projectors

When light energy is added, When light energy is added, a color appears brightera color appears brighter

The additive primary colours The additive primary colours are (RGB):are (RGB):

– – RedRed – Green – Green – Blue – Blue

Secondary colours produced are (CMY) Secondary colours produced are (CMY)

– – Cyan – Magenta – YellowCyan – Magenta – Yellow

Different percentages of red, green, & blue light are used to Different percentages of red, green, & blue light are used to generate different coloursgenerate different colours

White White light is created when Red, Blue and Green are mixed light is created when Red, Blue and Green are mixed togethertogether

There is no way of making black by adding red, green and There is no way of making black by adding red, green and blue light sources, the screen must be black to start with.blue light sources, the screen must be black to start with.

http://dev.physicslab.org/asp/applets/additivecolors/default.asp

Our EyesOur Eyes

Our eyes use the additive colour Our eyes use the additive colour approach, but how do we see approach, but how do we see colour if all wavelengths are colour if all wavelengths are coming in from the sun (white coming in from the sun (white light)?light)?

Green Surface

White lightGreen Light reflected

Blue Surface

Blue Light reflectedWhite light

White light

Black Surface

No Light reflected

Red Surface

White light Red Light reflected

White Surface

White lightWhite Light reflected

Objects absorb all colors except the color being seen, which is reflected

Objects absorb all colors except the Objects absorb all colors except the color being seen, which is reflectedcolor being seen, which is reflected White surface = all wavelengths (blue, red, White surface = all wavelengths (blue, red,

green) are being reflectedgreen) are being reflected Black surface = all wavelengths are being Black surface = all wavelengths are being

absorbed.absorbed. Red surface = blue and green Red surface = blue and green

wavelengths are absorbed, red is reflectedwavelengths are absorbed, red is reflected Green surface = blue and red wavelengths Green surface = blue and red wavelengths

are absorbed, green is reflected. are absorbed, green is reflected.

DEMO

Questions, why are clouds Questions, why are clouds white?white?

Why is it not a good idea to Why is it not a good idea to wear black in the summer?wear black in the summer?

Subtractive Color ModelSubtractive Color Model Used in the print media Used in the print media

ex. inks, fabrics, paints, crayons, etc.ex. inks, fabrics, paints, crayons, etc.

When more color is added, When more color is added, a color appears darkera color appears darker

The subtractive primary colours are (CMY):The subtractive primary colours are (CMY):

– – CyanCyan

– – MagentaMagenta

– – YellowYellow

Secondary colours produced by CMY colours are Secondary colours produced by CMY colours are

– – RedRed

– – GreenGreen

– – BlueBlue

Different percentages of cyan, magenta & yellow light Different percentages of cyan, magenta & yellow light are used to generate different coloursare used to generate different colours

There is no way of making white by adding CMY colour There is no way of making white by adding CMY colour sources, the paper/canvas must be white to start with.sources, the paper/canvas must be white to start with.

What do you notice about the

primary & secondary colours?

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Computers DON’T use the subtractive theory.

Because printers work on subtractive colour

system and computers don’t, it’s hard to

reproduce the same picture.

Cookie WheelCookie Wheel

Colour BlindnessColour Blindness 1 out of 10 men and 1 out of 200 1 out of 10 men and 1 out of 200

women have some type of color women have some type of color deficiency. deficiency.

The most common type is The most common type is mistaking red and green.mistaking red and green.

The second most common type The second most common type is mistaking blue and yellow is mistaking blue and yellow

Blind Spot – not just on Blind Spot – not just on cars!cars!