Year 9 - Computing
File size of digital images
Data representation: images and sound
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This pupil-friendly study guide includes a unit summary, clear notes, common mistakes, and quick questions with answers.
Unit Summary
In this unit, pupils will focus on digital media such as images and sounds, and discover the binary digits that lie beneath these types of media. They will explore how images and sound can be manipulated and consider the link between quality of images and sound and the resulting file size.
Lesson Summary
You will learn to describe how image file sizes are calculated and how changes to image quality and colour accuracy adjusts this.
Key Notes
- The colour of each element in a digital image is represented using binary digits.
- Changing image quality (resolution) affects file size: higher quality increases size, lower quality decreases it.
- Changing colour depth affects file size: higher colour accuracy increases size, lower accuracy decreases it.
Vocabulary To Learn
- resolution: total amount of pixels an image contains based on its width and height expressed in pixels
- colour depth: the number of bits used to represent the colour of each pixel, which is also known as bit depth
- file size: a measure of how much binary data a file contains
Common Mistakes To Avoid
- 1 bit is always used to represent 1 pixel.
3 Quick Questions (With Answers)
1. Describe the system or process from this lesson in clear steps.
The colour of each element in a digital image is represented using binary digits. Changing image quality (resolution) affects file size: higher quality increases size, lower quality decreases it.
2. Define this computing term and give one practical example. 'resolution'
total amount of pixels an image contains based on its width and height expressed in pixels. Add one real device or system example to prove understanding.
3. Correct this common computing misconception.
Mistake: 1 bit is always used to represent 1 pixel. Correction: While bits are used to represent the colour of pixels, it's not always a one-to-one relationship. The number of bits used can vary depending on the colour depth of the image.
More Lessons In This Unit
Browse all guides in the Year 9 Computing guide library.