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How Cameras Work

 

 

To make sense out of digital photography we need to talk first about photography in general. The only important difference between a film camera and a digital camera is that the film camera captures its image on film and the digital camera captures its image on an array of electronic sensors.

A film camera momentarily opens its shutter to light, which makes chemical changes in a thin coating (emulsion) of silver bromide on top of a plastic film strip. When the film is developed and fixed, what's left behind is a pattern of silver grains.

A digital camera momentarily opens its shutter to light, which falls on a large array of very tiny charge coupled devices (CCDs) or complementary metal-oxide semiconductors (CMOS). The light generates a voltage in each of the millions of CCD or CMOS sensors and the camera very quickly scans the array and records the result on a digital memory card.

In a digital camera each sensor is called a "picture element," which gets shortened to "pixel." But if you look closely enough at the image on a film negative you'll see that the silver grains are pixels too. One difference between the two collections of pixels is that unless you have a digital camera with around 11 or 12 million sensors in its sensor array, the film will have more pixels. Another difference is that if you're shooting color the film will have layers separated by filters. During processing, color dyes are added to the appropriate layers. In a digital camera each pixel digitally produces information that includes both brightness and color.