Digital Photography 101
Chapter 1: Introduction to Film and Digital Cameras
1.4: How a digital camera works
The digital camera was originally developed by NASA to send images
back from outer space. It has been the advent of personal computers
and the internet that has made them mainstream image-capturing devices.
The principals of the light tight box are the same except the
light sensitive surface is no longer film but has now become an
electronic device called a CCD or Charged Coupled Device.
A Charge Coupled Device is one of the two main types of image
sensors used in digital cameras. When a picture is taken, the CCD
is exposed to light coming through the camera's lens. Each of the
thousands or millions of tiny pixels that make up the CCD converts
this light into electrons. The number of electrons, usually described
as the pixel's accumulated charge, is measured, and then converted
to a digital value, which also records the colour values.
This image data is then stored on a chip in the form of digital
memory. This is an example of an external memory card used in digital
SLR cameras. This card will hold 512 Megabytes of data, which equates
to about 140 jpg files at six million pixels.
We will look at resolution next.
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