Refraction of Light • If the light wave is travelling at an angel and the speed of light travels in a different angle, the wave will be bent, or refracted. Refraction of Light • Prisms and water droplets refract light in the same way. The Visible Light Spectrum • What would you expect to see if white light was sent through a prism? • Lights of different colours (red, green, and blue) shine through! • You have just split white light into the visible light spectrum. Watch: https://www.youtube.com/watch?v=x8FZ7 Tu98Yo • Colour is created from wavelengths of light. • Red has the longest wavelengths, 630650 nanometers. • Blue and purple have the shortest wavelengths, 380-480 nanometers. • We have two kinds of light receptors in the back of our eye that help us see colour. • Cones – help us see colour • 6-7 million per eye • Rods – help us see in dim light (black or white) and to use our peripherals (looking from side to side) • Over 120 million per eye. The Visible Light Spectrum • Light is made up of energy waves which are grouped together in a spectrum. • Our eyes can only see the visible light spectrum. The Visible Light Spectrum Watch the following: https://www.youtube.com/watch?v= pvC9MQvqHMQ The Colour Theories • All the colours of the rainbow can be made from red, yellow and blue. • So why do we see more colours than that? • It has to do with the mixing and taking away of colours, otherwise known as Additive and Subtractive Colour Theories. Additive Colour Theory Additive Colour Theory • The additive color theory involves light emitted directly from a source (ex. a television) • When various amounts of red, green, and blue light are added together they produce other colours. Additive Colour Theory • If you add the primary colours of light together, you can reliably make secondary colours. Additive Colours • Primary Colours • Secondary Colours – Red (R) – Green (G) – Blue (B) – Yellow (Y) – Magenta (M) – Cyan (C) Additive Colour Theory • When all of the primary colours are added together they make white light. • This is why the middle of the picture below is white. Visualize Additive Colour • Imagine three spotlights, one red, one green and one blue are shone on a skater. Where the blue and green spotlights overlap, the color cyan is produced; where the blue and red spotlights overlap, the color magenta is produced; where the red and green spotlights overlap the color yellow is produced. When added together, red, green and blue lights produce what we perceive as white light. Complimentary Colours • Complimentary colours are any two colors that when added together, produce white light. What are the complimentary colours here? Red and Cyan Green and Magenta Blue and Yellow Additive Colour Theory Watch the following: https://www.youtube.com/watch?v=t8ifzy-FSC8 Stop when it starts talking about subtractive colour theory. OR do the demonstration. Applications: Additive Colour • Television is based on additive colour theory. • So is theatre lighting! Applications: Additive Colour • Television screens and computer monitors: – Thousands of red, green and blue phosphor dots make up the images on video monitors. – The phosphor dots emit light when activated electronically, and it is the combination of different intensities of red, green and blue phosphor dots that produces all the colors on a video monitor. – Because the dots are so small and close together, we do not see them individually, but see the colors formed by the mixture of light. In Summary • Additive color involves the use of colored lights. It starts with darkness and mixes red, green, and blue light together to produce other colors. When combined, the additive primary colors produce the appearance of white. Homework Questions: What combination of colours would you need to: 1. Set a light blue “mood light” on an actor in a tranquil theatre scene? 2. Cast a yellow “daytime” light in your home? 3. Make a white light if you only had a cyan filter? 4. Make a white light if you only had a green filter? 5. Turn magenta into blue? 6. Turn green into yellow? 7. Turn yellow into red? Subtractive Colour Theory • Subtractive colour theory says that if you remove primary colours from white light, you can reliably make other colours. • This is the way we “normally” think of mixing colours! 17 February 2019 Subtractive Colour Theory • Primary colours are subtracted when they are absorbed by a surface. • What is reflected by the surface is the colour we see. 2/17/2019 For example: an apple really has no color; it emits no light energy of its own. An apple reflects the wavelengths of light that cause us to see red and absorbs the other wavelengths, which makes us see red. Subtractive Colour Theory • Subtractive color starts with an object (such as paper or canvas) that reflects light. • Colorants (such as pigments or dyes) on the object reflect certain wavelengths of light. • The wavelengths that are absorbed into the object are “subtracted”. We see what is reflected. Subtractive Colour Theory • If an object reflects all of the white light, it appears white. • If an object absorbs (subtracts) all the light, it appears black. Subtractive Colour Pigments • Pigments are dyes or paints that absorb different colours: – For example, a red car absorbs green and blue, and reflects red. • Y+C=G • Y+M=R • C+M=B Subtractive Colour Filters Filters are transparent, allowing light to pass through them. Some light is absorbed by the surface below the filter, and some is reflected. • Primary Colours: – – – • Secondary Colours – – – • Red (R) Filter = Absorbs G - B Green (G) = R - B Blue (B) = R – G Magenta (M) = G Cyan (C) = R Yellow (Y) = B Tints and Shades: – – White: Clear Filter Black: Opaque Filter Subtractive Colour Theory • Watch the following: https://www.youtube.com/watch?v=t8ifzy-FSC8 Begin from where you left off – when it starts talking about subtractive colour theory. Applications: Subtractive Colour • Printers use color inks that act as filters and subtract portions of the white light. • Printing inks are transparent, allowing light to pass through to and reflect off of the paper. • The printing process uses cyan, magenta and yellow inks, and a fourth ink, black. • Each process printing ink (cyan, magenta, yellow) absorbs or subtracts certain portions of white light and reflects other portions back to the viewer Applications: Subtractive Colour • • • • • Paints Clothing and food dyes Photography Newspapers, magazines Printers In Summary • Subtractive color involves colorants and reflected light. It uses cyan, magenta and yellow pigments or dyes to subtract portions of white light illuminating an object to produce other colors. When combined in equal amounts, pure subtractive primary colors produce the appearance of black. 2/17/2019 Homework Questions Suppose you’re working on a newspaper, and are printing the centre spread. What would you need to do to produce: 1. The bright red of an apple? 2. The colour of the afternoon sky? 3. The green leaves of a tree? 4. The deep blue of a dragonfly’s body? 5. The white of snow?