What is a pixel?
A pixel is the smallest addressable physical element of a digital image or display device. The term is abbreviated as px and is also referred to as a pel or picture element (PE). In digital imaging, pixels are arranged in a regular two-dimensional grid. Each pixel represents one sample point of an original image and holds a specific color or intensity value.
In color imaging systems, a pixel's color is typically described by three component intensities: red (R), green (G), and blue (B).
Etymology
The word pixel combines pix (from "pictures," shortened to "pics") and el (for "element"). Related compound words using the same el suffix include voxel (volume pixel) and texel (texture pixel).
History of Pixels
The concept underlying the pixel emerged alongside the earliest developments in television and digital imaging. Paul Nipkow's 1888 German patent used the term "Bildpunkt" to describe discrete picture points in his mechanical television scanning system.
The term "picture element" appeared in Wireless World in 1927. Early U.S. patents addressing the transmission of moving images referenced the same concept from as early as 1911.
During the 1950s and 1960s, researchers working on computer graphics and digital imaging needed a standardized way to represent and store visual information. This need produced the pixel as a discrete unit of an image, characterized by position and intensity. Frederic C. Billingsley formally introduced the word "pixel" into published literature in 1965 through JPL's work on space probe imagery.
How do pixels work, and how are they used?
Pixels work by storing and displaying discrete color and intensity values at specific positions in a two-dimensional grid. Each pixel holds a numeric value or set of values that corresponds to a color.
The number of pixels determines the resolution of a computer monitor, TV screen, or digital image.
Common display resolutions include:
- 480p (standard definition): 640 × 480 pixels, used for small mobile devices
- 720p (HD): 1280 × 720 pixels
- 1080p (Full HD): 1920 × 1080 pixels
- 1440p (QHD): 2560 × 1440 pixels, common in PC gaming monitors
- 4K (Ultra HD): 3840 × 2160 pixels, offering four times the pixel count of 1080p
- 8K: 7680 × 4320 pixels, with 16 times the pixel count of 1080p
How big is a pixel?
The physical size of a pixel depends on the resolution setting of the display and the size of the screen. A pixel does not have a fixed size in millimeters. The same 3000 × 2000 pixel image appears larger on a 27-inch monitor and smaller on a 5-inch smartphone screen.
Pixel in Computer Graphics
In computer graphics, including video games and computer-aided design (CAD), pixels form the foundation on which all visual output is built. Rendering engines process pixels in real time to simulate lighting, shading, and texture effects.
Pixel in Digital Photography
In digital photography, each pixel on a camera's image sensor is a light-sensitive photo site. These photo sites are arranged in a grid and capture incoming light, converting photon energy into electrical signals.
The Pros and Cons of High Pixels
Advantages of High Pixels
- Finer Detail Capture: High-resolution sensors record more visual information per frame, useful for landscape, architectural, and product photography.
- Greater Cropping Range: Images with more pixels can be cropped heavily while retaining adequate resolution for print or screen output.
- Large-Format Printing: Higher pixel counts maintain sharpness at larger print dimensions, such as A1 posters or billboard graphics.
Limitations of High Pixels
- Larger file sizes: High-resolution images occupy more storage and require more processing power during editing.
- Higher demands on lenses: A high-resolution sensor reveals lens imperfections, including softness at the edges, chromatic aberration, and diffraction at small apertures.
- Amplified camera shake: The same degree of camera movement produces more visible blur on a high-resolution sensor than on a lower-resolution one.
- Increased noise in low light: Packing more pixels into the same sensor area reduces the physical size of each photosite, which captures less light per pixel and produces more noise in dark conditions.
Examples of Pixel
Smartphone displays demonstrate modern pixel density at scale. A flagship smartphone with a 1080p or 1440p display at a 6-inch diagonal screen size achieves a pixel density exceeding 400 PPI. At that density, individual pixels are not visible to the human eye at normal viewing distance, producing a sharp and smooth visual experience for text, photos, and video.
Conclusion
A pixel is the smallest addressable physical element of a digital image or display device, described by a specific color or intensity value composed of red, green, and blue component intensities. Pixels form the foundation of digital imaging across cameras, displays, medical scanners, telescopes, and computer graphics systems.