How digital images are made of pixels — Technology, 14–17 years
A digital photo is a grid of tiny coloured samples called pixels. More pixels can show finer detail, but image quality also depends on colour information, focus and the screen or camera.
A picture as a grid
Zoom in far enough on a digital image and you can see tiny squares of colour. Each square is a pixel, and the image is a grid where every pixel stores a colour value. Your eyes blend neighbouring pixels into lines, surfaces and recognisable objects.
Why pixels and resolution matter
Computers need a precise way to store and display a picture, so they sample it at positions in a grid. Resolution is the number of pixels across and down, such as 1920 × 1080. Higher resolution can preserve more detail, but it also needs more storage and processing.
Worked example: counting pixels
A small image is 4 pixels wide and 3 pixels high. Multiply the dimensions: 4 × 3 = 12 pixels in total. If each pixel can be red, green or blue with 256 levels, one simple colour model uses 3 bytes per pixel, so the colour data needs 12 × 3 = 36 bytes.
More pixels are not everything
It is tempting to think that doubling the pixel count always makes a photo twice as sharp. More pixels help only if the camera, focus and lens captured extra detail; otherwise they may just record a larger blurry image. Resolution describes the grid, not the whole quality of a picture.
Where digital images appear
Phone cameras, medical scanners, satellite maps and video games all turn measurements into grids of pixels. When an image is enlarged, software estimates colours for new positions, which can make edges look softer. The same idea also lets screens display photographs, diagrams and films.
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