A pixel is the smallest unit of information in a digital image or display.
The word pixel comes from the combination of pix, short for picture, and element. Therefore pixels are picture elements – the building blocks used to create digital images. The term was coined in the early 1960s, though no one is certain exactly where the term “pixel” came from.
A pixel is not a measure of physical size, it is a measure of resolution. Digital images and displays with high resolution contain many pixels while images and displays with low resolution contain fewer pixel.
Since pixels are not a measure of physical space, most computer displays are capable of being adjusted to contain a range of pixels. A common screen resolution is 1366 x 768 pixels (1366 pixels wide by 768 pixels tall). Displays designed for this resolution can often also accommodate resolutions of 1280 x 720, 800 x 600, and several other resolution settings.
Image resolution is also described in pixels. An image with a resolution of 800 x 600 pixels will naturally fill a display set to a resolution of 800 x 600 pixels. If the display resolution were increased to 1366 x 768 pixels, the image would shrink in physical size and no longer fill the entire screen. If a computer user stretched the 800 x 600 pixel image so that is filled a 1366 x 768 pixel display, the pixels making up the image would become visible, and the image would appear to be blurry as individual pixels became visible – the image would pixelate.
Also See: Resolution
Frequently Asked Questions
What is a megapixel?
The term megapixel is a measure of resolution where a single megapixel is equivalent to one million pixels. For example:
- 100 pixels x 100 pixels = 10,000 pixels or .01 megapixels
- 1000 pixels x 1000 pixels = 1,000,000 pixels or 1 megapixel
- 1366 pixels by 768 pixels (a common screen resolution) = 1,049,088 pixels or 1.05 megapixels.
What does it mean that I have a 12-megapixel camera?
A 12-megapixel camera will capture images with a resolution equal to approximately 12 million pixels. Generally speaking, a 12-megapixel image will be 4200 pixels wide by 2800 pixels tall.
What resolution is “good enough”?
The resolution of a digital space has to be related to physical size to determine if it will appear sharp or pixelated. Pixels per inch (PPI) is the term used to tie resolution to a physical measurement. PPI is a measure of the number of pixels rendered in a one-inch line on a display.
One common screen resolution, 1366 x 768, is used for laptop screens ranging in size from 11.1 to 15.6 inches. On a 15.6″ laptop screen with the resolution set to 1366 x 768, approximately 100 pixels are lined up side-by-side in a 1-inch span (100 PPI). At the same time, on an 11.1″ laptop screen the same resolution will result in approximately 140 PPI as the same number of pixels are squeezed into a smaller physical space.
100 PPI is the standard used for normal computer displays. When resolution falls very far below 100 PPI, the image begins to become excessively pixelated. As a result, 1366 x 768 is not commonly used for displays larger than 15.6″. For high-quality images, and for images intended for printing, the standard used is 300 PPI – above which the human eye is nearly incapable of making out individual pixels.