What is a pixel

What is a Pixel?

A pixel - short for picture element - is a single point in a digital image. Every digital image is made up of a rectangular grid of pixels arranged in rows and columns. Each pixel stores a colour value, and together the full grid of pixels forms the complete image that appears on screen.

Pixels are the smallest unit of a digital image. They are not visible under normal viewing conditions, but if you zoom in far enough on a digital photograph or screenshot, you will begin to see the individual coloured squares that make up the image. This is sometimes called pixelation.

How Pixels Form an Image on a Display

A display screen is itself divided into a grid of tiny light-emitting points, each corresponding to one pixel. When an image is shown, each pixel on the screen is set to the colour value stored for the corresponding pixel in the image. The display draws the image line by line, top to bottom, lighting up each pixel in turn until the full image is visible.

The number of pixels in an image - its resolution - directly affects how sharp or detailed the image appears. More pixels mean more detail. The two tabs below illustrate how the same subject looks at very different pixel counts.

Low Resolution - Few Pixels

An image with a small number of pixels - for example, 8 × 8 = 64 pixels total - displays with very little detail. Each pixel must represent a large area of the original subject, so fine detail is lost. Individual pixels become visible as coloured blocks, producing a blocky or blurry appearance. This is called pixelation and is a clear sign that resolution is too low for the display size.

High Resolution - Many Pixels

An image with a large number of pixels - for example, 1920 × 1080 = 2,073,600 pixels - can represent fine detail accurately. Each pixel covers only a tiny area of the subject, so edges appear sharp and colours transition smoothly. The individual pixels are too small to distinguish at normal viewing distances, giving the impression of a continuous, photographic image.

 Key Takeaways

  • A pixel (picture element) is the smallest single point in a digital image.
  • Every digital image is a rectangular grid of pixels; each pixel stores a single colour value.
  • A display screen lights up each pixel in turn to reproduce the image visually.
  • More pixels in an image means higher resolution and finer detail; too few pixels results in visible pixelation.