What Exactly Is a Pixel?

When talking about televisions, all this 720p, 1080p, and 4K can seem a bit confusing, especially if you just want to watch a movie or TV show in the comfort of your home and have it look as good as possible. But having the image look as good as possible all boils down to the small building block called the pixel, a word that most people have heard about, but not one that many fully understand. 

“Pixel” is a term derived from the words “picture” and “element,” and is the smallest representative unit of a digital image. Pixels are normally situated in a two-dimensional grid (like your television screen), and the number of pixels in that grid determines its overall resolution.

These primarily square or rectangular-shaped units were first designated in 1965 by American engineer Frederic C. Billingsley who, while working at CalTech’s Jet Propulsion Laboratory, described small pixels in images sent back to earth from NASA space probes exploring the moon and Mars. Pixels as a photographic concept have had a long and complicated history but can trace their origins back to German inventor Paul Nipkov’s concept of the “Bildpunkt,” or the dissected image of a “picture point.” Nipkov used this concept when he patented the world’s first mechanized television system way back in 1884. 

Current high-definition televisions are situated in two common fixed arrangements for pixel resolution, the minimum of 720p or maximum of 1080p (in this case the “p” does not stand for “pixel,” but we’ll get to that in a moment). The 720 refers to 1280 x 720, or the horizontal and vertical numbers of pixels on a given screen. Likewise, the 1080 refers to a standard horizontal count of 1920 x 1080 vertical count of pixels in the grid. Multiplied together, these numbers of pixels indicate the maximum amount of image detail found on your screen, which is important for the sharpness and level of vivid detail able to be seen on modern HD-TVs. Contrasted to the over 2 million pixels in a 1080p screen, old standard definition screens had around 300,000 pixels, which displayed a less detailed, much blurrier picture.

Though it may be slightly confusing, the “p” in 720p or 1080p stands for “progressive-scan,” and refers to the way the complete high-definition picture is sent to the pixels that make up your screen all at a single time. The opposite of progressive-scan is the outdated “interface-scan,” represented as “i,” which projects its picture into two separate fields on a TV screen at different times, thus causing the slight flickering effect seen on old television sets.

The resolution on consumer electronics like TVs will only get higher, and with the advent of 4K resolution—screens with at least 4,000 pixels in a horizontal grid that packs in four times the pixels of a 1080p screen—digital images will continue to improve and become more realistic in color and crispness. But just remember, it all comes down to one small but essential component—the pixel.