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Pixel in digital photography has multiple meanings.

Image sensor[]

In the context of the image sensor in digital cameras a pixel is a light sensitive element in an image sensor, typically a photodiode. Modern image sensors have tens of millions of pixels, or tens of megapixels. Overlayed on top of the image sensor on regular cameras is a colour filter array (CFA) which limits each pixel to receive just a part of visible wavelength spectrum - the most common CFA has two "green" sensitive pixels for each "red" and "blue" sensitive ones.

The more pixels there are, the better the image quality potential generally is. More pixels allows for finer sampling of the image that the lens draws, thus more details are visible. This not only allows for larger prints, but even smaller prints tend to get benefits from increased number of pixels. Because there is a CFA on top of the image sensor, a coarse sampling may manifest itself in unwated artifacts, like different forms of aliasing - a good example is the "moire" effect.

The main drawback of increase in the number of pixels is increase in image processing requirements - this can lead to slower operational speed and reduced battery life of a camera. Additionally memory and storage requirements are increased.

A Megapixel is a million pixels - occasionally abbreviated to Mpx or Mp. Typical digital cameras have resolutions specified in megapixels.

The "native" resolution of a camera is determined by the resolution - or number of pixels - of the image sensor, although some cameras use software to interpolate their sensor images into higher resolution pictures.

While almost all image sensors have a CFA on top the the pixel array - there are some exaptions. Some marginal cameras operate without colour separation - the compensation for this is aproximate 1 stop increase in light sensitivity and reduction in aliasing artifacts. The drawback is obviously the lack of colours. Another exception the the Foveon image sensor used by some Sigma cameras - instead of CFA Foveon sensor has three photodiodes at each pixel site at different depths in the silicon. It relies on the fact that different wavelengths of light tend to be absorbed at different depths - this is a probabilistic process, so the colour separation done this way is very weak and leads to relatively inaccurate colours and increase in noise. The benefit is reduced aliasing and slightly higher resolution for the same number of pixels.

Other contexts[]

Pixel is also a concept in both output formats, like JPG images - typically the number of pixels is the same that the camera has, though in this case each pixels has red, green and blue information - often JPGs are downsampled to smaller sizes with fewer pixels as for most use cases the smaller file sizes and smaller processing requirements of smaller JPGs far outweight the maximum details of the original size.

Also computer displays, televisions and other devices have pixels.