Color Theory

Which colours is white light made of?

Color Mixing Color can be perceived either from 1) a luminous object (TV, monitor, projector) using the Additive Approach 2) reflected pigment or ink (printouts, materials) using the Subtractive Approach

Additive Color Model Used by luminous objects ex. Computers, TV, projectors Used by luminous objects ex. Computers, TV, projectors When light energy is added, a color appears brighter When light energy is added, a color appears brighter The additive primary colours are (RGB): The additive primary colours are (RGB): – Red – Green – Blue Secondary colours produced are (CMY) Secondary colours produced are (CMY) – Cyan – Magenta – Yellow – Cyan – Magenta – Yellow

Different percentages of red, green, & blue light are used to generate different colours Different percentages of red, green, & blue light are used to generate different colours White light is created when Red, Blue and Green are mixed together White light is created when Red, Blue and Green are mixed together There is no way of making black by adding red, green and blue light sources, the screen must be black to start with. There is no way of making black by adding red, green and blue light sources, the screen must be black to start with.

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Our Eyes

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

Green Surface White light Green Light reflected Blue Surface Blue Light reflected White light Black Surface No Light reflected Red Surface White light Red Light reflected White Surface White light White Light reflected Objects absorb all colors except the color being seen, which is reflected

Objects absorb all colors except the color being seen, which is reflected Objects absorb all colors except the color being seen, which is reflected White surface = all wavelengths (blue, red, green) are being reflected White surface = all wavelengths (blue, red, green) are being reflected Black surface = all wavelengths are being absorbed. Black surface = all wavelengths are being absorbed. Red surface = blue and green wavelengths are absorbed, red is reflected Red surface = blue and green wavelengths are absorbed, red is reflected Green surface = blue and red wavelengths are absorbed, green is reflected. Green surface = blue and red wavelengths are absorbed, green is reflected.

DEMO

Questions, why are clouds white? Questions, why are clouds white? Why is it not a good idea to wear black in the summer? Why is it not a good idea to wear black in the summer?

Subtractive Color Model Used in the print media ex. inks, fabrics, paints, crayons, etc. Used in the print media ex. inks, fabrics, paints, crayons, etc. When more color is added, a color appears darker When more color is added, a color appears darker The subtractive primary colours are (CMY): The subtractive primary colours are (CMY): – Cyan – Magenta – Yellow

 Secondary colours produced by CMY colours are – Red – Red – Green – Green – Blue – Blue Different percentages of cyan, magenta & yellow light are used to generate different colours Different percentages of cyan, magenta & yellow light are used to generate different colours There is no way of making white by adding CMY colour sources, the paper/canvas must be white to start with. There is no way of making white by adding CMY colour sources, the paper/canvas must be white to start with. What do you notice about the primary & secondary colours?

16 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 Wheel

Colour Blindness 1 out of 10 men and 1 out of 200 women have some type of color deficiency. 1 out of 10 men and 1 out of 200 women have some type of color deficiency. The most common type is mistaking red and green. The most common type is mistaking red and green. The second most common type is mistaking blue and yellow The second most common type is mistaking blue and yellow

Blind Spot – not just on cars!