How digital images use pixels — Technology, 11–13 years
A digital picture is built from tiny coloured squares. Pixels explain why images can look sharp, blurry, large or small.
The idea
A digital image is a grid of tiny points called pixels. Each pixel has a colour, and all the colours together make the picture we see. More pixels can show finer detail, but the result also needs more space to store.
Why it was needed
A device needs a practical way to store and display a picture. A grid turns the picture into many small, measurable pieces instead of asking the device to remember every curve perfectly. This makes images possible on screens, cameras and printers, although some detail is lost.
A worked example
Suppose a picture is 800 pixels wide and 600 pixels high. First, calculate 800 × 600 = 480,000 pixels. If each pixel uses 3 bytes for its colour, the uncompressed picture needs 480,000 × 3 = 1,440,000 bytes, about 1.44 megabytes.
The common trap
It is tempting to think that making a picture bigger creates more detail. Enlarging it usually spreads the same pixels over more space, so the edges look blocky or blurry. The mistake is reasonable because the picture really does become larger, but its original information has not increased.
Where it appears
Pixels appear in phone photographs, video games, maps, scans and digital art. A camera with more pixels can record finer detail, while a screen with more pixels can show a sharper picture. Other choices, such as lenses, lighting and compression, also affect what we see.
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