- Define and explain Images and Pixels in your own words
- Use key terms such as pixel accurately
- Apply what you have learned to new examples and questions
- Avoid the common mistakes learners make with this topic
This lesson focuses on Images and Pixels: discover how grids of coloured dots become photographs.
Discover how grids of coloured dots become photographs.
Key ideas
Everything is binary underneath
Text, images, sound and video are all stored as patterns of bits — the computer just interprets the patterns differently. The binary pattern 01000001 means the letter 'A' in text, but the same pattern could mean the number 65 or a dark pixel in an image. Meaning comes from context, not from the bits themselves.
More bits means more detail
With n bits you can represent 2 to the power of n different values: 8 bits give 256 colours or characters, while 24 bits give over 16 million colours. Higher colour depth, higher image resolution and higher sound quality all cost more bits — a trade-off between quality and file size.
Key term — pixel: The smallest dot in a digital image. Images are grids of pixels, each stored as a binary colour value.
The letter 'A' is stored as 01000001. What number is that in denary, and why might the same pattern mean something else elsewhere?
65 — and the same bits could be a colour value or part of an image, because meaning comes from how the program interprets the bits.
Answer: 65 — and the same bits could be a colour value or part of an image, because meaning comes from how the program interprets the bits.
- Confusing resolution with colour depth Correction: resolution is how many pixels an image has; colour depth is how many bits describe each pixel — both affect file size, but they are different things.
- Reading binary left to right as if the leftmost digit is worth 1 Correction: the rightmost column is always worth 1 — write the place values above the digits before adding.
Practice
13 — that is 8 + 4 + 1.
10100 — that is 16 + 4.
16 — from 0 to 15.
A higher rate takes more samples every second, so more numbers must be stored — better quality costs more bits.
Quick check
Which of these best defines "pixel"?
True or false: adding one more bit to a code doubles the number of values it can represent.
- Images and Pixels: discover how grids of coloured dots become photographs.
- Everything is binary underneath: Text, images, sound and video are all stored as patterns of bits — the computer just interprets the patterns differently.
- bit: A single binary digit — a 0 or a 1.
- Watch out for: confusing resolution with colour depth