Week 1 - Perception & Images Flashcards
What is Multimedia?
• Using more than one medium of expression, communication.
An interactive computer-mediated presentation that includes at least two of the following:
- Text
- Sound
- Still graphic images
- Motion graphics
- Animation
What two functions do multimedia computers serve?
- Development tools for the creation of multimedia productions e.g. Adobe, Apple, Microsoft, Unity.
- Delivery devices for multimedia applications
- Browsers or player applications.
What is Perception?
The consciousness or awareness of objects or other data
through the medium of the senses.
What is the Electromagnetic Spectrum?
• Wide range of
waveforms known as the electromagnetic spectrum.
What is the speed of light?
- Electromagnetic waves travel at the speed of light
- c = 299,792,458 m/s
- c = fλ
- 299,792,458 m/s / 1,800,000,000Hz = 0.17m
- 0.17m is the wavelength (λ) of what?
What 3 things is the power of light measured by?
- Radiance (watts)
- Luminance (lumens)
- Brightness
What is Radiance (watts)?
• Total amount of energy emitted
What is Luminance (lumens)?
• Light strength that is perceived by
the human eye
What is Brightness?
• Subjective measure of how bright an object
appears to be
State the order of the electromagnetic spectrum highest energy to lowest energy. • G • X • U • V • I • M • U • R
- Gamma rays
- X-rays
- Ultra-violet
- Visible
- Infra-red
- Micro-waves
- UHF/VHF/TV
- Radio waves
Which electromagnetic element has the highest energy but shortest wavelength?
• Gamma rays
Which electromagnetic element has the lowest energy but longest wavelength?
• Radio waves
What is the wavelength of visible light between?
• 400-700 nanometers
State the 2 light-receptor cells in the retina?
- Rods
* Cones
What are rods in the retina?
- Detect shades of black & white.
- In the peripheral vision.
- Work in low light - night vision.
- Approx 120 million of them.
Describe cones in the retina?
- Sensitive to colour.
- Mainly central.
- Only work in bright light.
- Only sensitive to RGB.
- Approx 6-7 million
Humans are tri -_________ & respond to light in bands of RGB.
• Tri-chromatic
What are active sources of colour?
• Emitting different wavelengths of light
e.g. from monitors/projectors.
What are passive sources of colour?
• Absorbing some wavelengths & reflecting others.
e.g. from printed documents
What are the primary colours of active displays?
- Red
- Green
- Blue
What are the primary colours of passive displays?
- Cyan
- Magenta
- Yellow
On a white background which colours of RGB are absorbed?
• None of the colours
On a cyan background which colours of RGB are absorbed?
• Red
On a Magenta background which colours of RGB are absorbed?
• Green
On a Yellow background which colours of RGB are absorbed?
• Blue
What is the intensity of each RGB colour to the eye?
• Red - 0.299
• Green - 0.587
• Blue - 0.114
=1
What is the Colour Gamut?
• Specifies the ranges of colours that can be produced by a particular display • Film Gamut • Monitor Gamut • Printer Gamut
What 3 things do human eyes respond to more than just dominant wavelength?
- Luminance or brightness
- Excitation purity or saturation
- The chromaticity or hue of light
State the 3 psychophysical models?
- Hue - pure dominant colour
- Lightness
- Saturation - how much the colour is diluted by white light
What is the HSV colour model?
• Mainly refers to the saturation and dominance of hue in the colour.
Describe digital images?
- Composed of pixels
* Picture resolution is no. of pixels used to make up image.
Another word for digital images?
• Bitmap images
Describe resolution?
- Amount of detail
* Storage requirements
What is the approx resolution compact cameras take?
• 10-24 megapixels
Describe aspect ratio?
• no. of horizontal pixels x vertical pixels
How are images stored?
- Pixels in images are assigned numerical values to store colour information.
- 0 or 1
Colour values range from?
• 0-255
Describe true colour?
- High quality
* Requires more memory
Describe palette colour?
- Limited numbers of colors
* Enables easier implementation of certain techniques