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Pixels: how screens make pictures — Technology, 7–10 years

A digital picture is built from many tiny coloured squares. Looking closely at pixels explains both sharp images and blocky ones.

Tiny coloured squares

A screen picture is a grid of pixels, short for picture elements. Each pixel receives a colour, and your eyes blend the nearby pixels into lines, faces and objects when you look from a normal distance.

Why use pixels?

A computer needs a simple way to store and change a picture. A grid gives every small place its own colour, so the machine can copy, edit or display the image without treating the whole scene as one mysterious object.

Making a tiny flag

Make a 3-by-2 picture. First draw six squares. Colour the top three blue and the bottom three yellow. The result has 6 pixels, 3 in each colour, so the screen can recreate this tiny flag by lighting those squares.

More pixels is not more zoom

It is reasonable to think that adding pixels simply makes a picture bigger, because more squares cover more space on paper. In fact, more pixels usually make more detail in the same space; zooming enlarges the view and may reveal the squares.

Cameras and games

Phone cameras turn light into coloured pixels, while games draw characters and landscapes on pixel grids. A small icon may use few pixels; a detailed photograph uses millions, so it can show finer edges and textures.

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