It is really hard to imagine how I am able to rewatch a moment of the past just because some fancy camera recorded it? If I think about it it feels very unnatural.
What are the key parts of microphones and cameras that make them work the way they work?
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Microphones and cameras have sensors that react to vibrations in the air and to light, generating an electrical signal in response. The device then measures that signal and notes it down over time. In analog devices, this was done by transcribing it as a magnetic signal onto a tape. In digital devices this done by measuring it as a very precise number, and storing those to memory of some sort.
To play back the sound or the video, a device takes the previously recorded measurements and converts them back to electrical signals, which get sent to either a speaker or to pixels on a screen, which then either vibrate the air or shine with a strength proportional to the original signal, recreating the original sound or picture.
Nowadays cameras use a CCD or charged couple device, which is basically a fancy sensor that turns photons into electric signals. By using a lens that bends light, a clear image can be made out of the light that enters the lens, and when that light hits the CCD the electrical signals are stored as digital code that can be reproduced as an image on a screen or as a picture from a printer.
Sound is captured by a microphone which has a little diaphragm that moves back and forth when sound waves hit it. That movement can be turned into analog electrical signals or digital ones then turned back into sound by moving another diaphragm with magnets. That moving diaphragm pushes against the air creating sound waves you can hear.
Microphones are basically speakers but wired to function backwards. When you speak into a microphone, you create sound waves that make a membrane inside of the mic vibrate, and the movement of that membrane causes an electrical signal to be sent down a wire into a Digital audio interface. This is a piece of equipment that takes in analog electrical signals and transforms them into digital signals. This digital signals are fed into a program that processes the audio and stores is in some format (mp3 wav etc…)
A camera works by taking a lens (or multiple lenses) to focus the light going into them to a specific spot inside the camera. This spot that the light is focused onto is a silicon chip made out of millions of tiny sensors laid out in a grid.
These sensors are able to detect the brightness and color of the light that is hitting them. And each sensor corresponds to a pixel in your picture.
When you take a picture, the camera opens its shutter allowing light to hit the sensors and then the sensors sends the information that they registered and the picture gets stored as an array of different values of brightness and color. The specifics of how this is done from a software point of view is beyond the scope of an ELI5.
For video, this process is repeated many times per second (usually 24 times per second at least) and then the pictures are shown back to you at that speed.
To put it more childishly, a camera is just a robot eye and a microphone is just a robot ear. They work according to roughly similar principles as their biological counterparts, except they’re also designed to save the input for review. If it’s the *recording* itself that’s blowing your mind, then you want to look into information theory.
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