The word analog or analogue recording comes from the Greek, ana "according to" and logos "relationship".
An analog or analogue signal is any continuous signal for which the time varying feature (variable) of the signal is a representation of some other time varying quantity, i.e., analogous to another time varying signal. For example, in an analogue audio signal, the instantaneous voltage of the signal varies continuously with the pressure of the sound waves. It differs from a digital signal, in which the continuous quantity is a representation of a sequence of discrete values which can only take on one of a finite number of values. The term analogue signal usually refers to electrical signals; however, mechanical, pneumatic, hydraulic, human speech, and other systems may also convey or be considered analogue signals.
Analogue recording is a technique used for the recording of analogue signals which, among many possibilities, allows analogue audio and analogue video for later playback.
Analog recording methods store signals as a continuous signal in or on the media. The signal may be stored as a physical texture on a phonograph record, or a fluctuation in the field strength of a magnetic recording. This is different from digital recording which digital signals are represented as discrete numbers.
Digital signals are a sequence of pulses consisting of just two states which are ON (1) or OFF (0). There are no numbers or values in between.Film can be a 'chemical' or digital process.
When it is a chemical process a light sensitive silver halife emulsion coated on a film base is exposed to light in a camera. This creates a latended image which is made visible by emerging the film into a chemical solution which we refer to as a 'developer'. A print can then be made by projecting the image from the film onto sensitized photographic paper and processing the paper through a number of chemical baths. A movie projector is an opto-mechanical device for displaying motion picture film by projecting it onto a screen.
Digital imaging does not require chemicals. Digital images are captured using arrays of photo sensors and these images are then processed by specialised software. Prints can be made through for traditional projection. Or the film can remain in a digital form for digital protection.
In everyday speak people commonly refer to chemical photography as analogue to contrast it with the digital process. Here, analogue is referring a signal whose output is proportional to the input.
A good example for analogue in traditional photography is a light meter where light falls on a photo cell which generates an electrical current moving a needle over a scale. The more bright the light is the more the needle moves. Ironically, the sensor in a digital camera is also analogue: each one of the millions of pixels which constitute the sensor is a light sensitive photo cell generating a tiny electrical current which is responding to light. The brighter the light the stronger the current.
Short YouTube video explaining the difference between Analog & Digital Signals:
Bibliography:
"Analog Recording". En.wikipedia.org. N.p., 2016. Web. 26 May. 2016.
https://en.wikipedia.org/wiki/Analog_recording
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