How a digital camera captures an image

We ,as humans,see light, but things(the retina) works within our eyes and convert light into signals, so that they can be transmitted to other parts of the body. For a camera, the same theory applies. How does it work without films as in traditional cameras? In my chemistry classes, I learnt that there is some silver chemical or something on the film, and when light falls on it, image is produced on the film.But for digital cameras the film is replaced by a semiconductor. Light falling on the semiconductor is used to store the image (SLR cameras have mechanisms for cleaning itself internally) The 'semiconductor' is called the sensor, which detects the presence of light. A sensor does the purpose of a retina of the eye. That is , it finds the presence of light, and converts into digital signals.

Usually a Charge Coupled Device (CCD) sensor is used in our 'point-and-shoot' cameras. It is nothing but something that converts light into electrons.It can be considered to be a 2-D array of light detecting cells. An Analog-to-Digital Converter(ADC) calculates the charge at each point(or cell) and converts into binary form.

A CMOS sensor

Another sensor used is 'Complementary Metal Oxide Semiconductor (CMOS)'. It does the same thing, but it does not need an ADC, because the signals produced are already digital. CCD sensors are used in our normal point-and-shoot cameras, while CMOS is used for high-end SLR's.

To put it in simple words, the camera converts light into an image in simple steps :

1. Light comes in through the lens
2. Falls on a light sensor
3. Sensor converts light into digital signals (In CCD sensor, an extra ADC converter is needed)
4. Converted to binary form
5. Stored as image