Starter quiz
- What is the basic unit of data in a computer system?
- byte
- binary digit (bit) ✓
- pixel
- character set
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- What does a character set do?
- matches colours to binary sequences
- represents image resolution
- represents file size
- matches characters to binary sequences ✓
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- Which character encoding system uses up to 32 bits per character?
- ASCII
- Unicode ✓
- RGB
- bitmap
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- Match the terms to their definitions:
- pixel⇔smallest element of an image ✓
- colour depth⇔number of bits used per pixel ✓
- resolution⇔total number of pixels in an image ✓
- byte⇔a group of 8 bits ✓
- How many states are possible with a sequence of 4 bits?
- '16' ✓
- What does colour depth quantify?
- the number of bits used per pixel ✓
- the number of colours in an image
- the resolution of an image
- the file size of an image
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Exit quiz
- Place the following file sizes in order from smallest to largest:
- 1⇔500 kB
- 2⇔1.3 MB
- 3⇔4000 kB
- 4⇔2 GB
- What determines the file size of a bitmap image?
- the colour depth ✓
- the type of file used to save the image
- the size of the display screen
- the resolution ✓
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- Match the terms to their definitions:
- trade-off⇔accepting a limitation to achieve a beneficial outcome ✓
- resolution⇔total number of pixels in an image ✓
- colour depth⇔number of bits used per pixel ✓
- low resolution⇔suitable for web use or thumbnails ✓
- high resolution⇔suitable for printing or detailed graphics ✓
- What happens when the colour depth of an image is increased?
- the file size decreases
- the file size increases ✓
- the resolution decreases
- the image becomes unusable
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- What is the effect of increasing the resolution of an image?
- the file size increases ✓
- the colour depth decreases
- the file size decreases
- the image quality becomes worse
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- Which of the following is a trade-off when reducing image resolution?
- higher file size for better quality
- lower file size for reduced quality ✓
- increased colour depth
- improved image quality
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Worksheet
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Presentation
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Video
Lesson Details
Key learning points
- The file size of a bitmap is determined from its colour depth and resolution.
- Increasing the colour depth of an image will increase its file size.
- Increasing the resoultion of an image will increase its file size.
- Selection of image resolution and colour depth depend on the use of the image and limitations imposed by the file size.
Common misconception
Using a low resoultion or colour depth for an image makes it unusable.
A low resolution or colour depth does not necessarily make an image unusable. It depends on the purpose. Lower settings can be suitable for web use, icons or thumbnails, while higher quality is needed for printing or detailed graphics.
Keywords
Trade-off - accepting a limitation to achieve a beneficial outcome
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