Pixel

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A digital photographic image is made up of an array of dots, called Pixels. Each pixel can be only one colour; the number of different colours available depending on the bit width of the storage format or image sensor (such as a CCD).

The maximum possible sharpness of an image is largely determined by the number of pixels used to store, display and/or print it; more pixels means smaller pixels, which can capture increased detail. Similarly, a wider bit width allows more colour differences to be rendered, and so better subtlety of tone. The number of pixels (or, more properly, the number and bit-width/colour-depth) is often called the resolution of the image. More pixels (and greater bit widths) can mean greater possible quality, but also raised memory or disk storage requirements and slower processing. Too few pixels can result in the pixels becoming noticeable in an image, which can show "jaggies" - jagged edges to lines.

A Megapixel is a million pixels. Typical digital cameras have resolutions specified in megapixels. The "native" resolution of a camera is determined by the resolution of the image sensor, although some cameras use software to interpolate their sensor images to higher resolution pictures.

Pixels in an image are usually square (i.e. the same width as height), and arranged in a rectangular grid. However, there are exceptions; some computer displays (e.g. the EGA "standard") have had rectangular pixels (e.g. taller than they are wide), and some image sensors (e.g. the Fuji Super CCD) have their pixels in non-rectangular grids. These exceptions are reasonably rare.