Analogue
The sensor of a digital camera is also analog. Each of the many millions of pixels which make up the sensor is a light-sensitive photocell which generates a tiny electrical current in response to light. The brighter the light, the stronger the current. Digital only comes into play when the brightness levels are coded into the binary system (the language of computers) to create an image file.
Figure: CCD : Charge Coupled Devic and process of analog convert
A CCD, or a Charged-Coupled Device, is a photosensitive analog device that records light as a small electrical charge in each of its pixels or cells. In essence a CCD is an collection of CCD cells.
The signal captured by the CCD requires additional circuitry to convert the analog light data into a readable digital signal.
Digital image
An image may be defined as a two dimensional function, f(x, y) where x and y are spatial (plane) coordinates spatial (plane) coordinates and the amplitude amplitude of f f at any pair of coordinates (x, y) is called the intensity or gray level of the image at that point
• When x, y, and the amplitude values of f are all finite, discrete quantities, we call the image a digital image
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