How does photography work? How do you take a moment in front of you and put it on paper and keep it forever?
In: Technology
Your eyes actually never see any “THING” that exists anywhere. All they detect is the light bouncing off those things. A camera simply captures the light bouncing off the things its pointed at in a very small span of time (the time it takes for the shutter to open and close again, roughly 1/60 of a second).
During the time the shutter is open, light enters the camera lens, and is refracted and focused onto some type of light detection device. In older film-based cameras this was literally a thin strip of plastic coated with tiny silver crystals in a gelatin. The crystals chemically react to light that hit them differently depending on the frequency and intensity of the light, (color and brightness). The result is a semi-transparent square in the same configuration of whatever light hit it at that time. Then, in the dark room, the strip of film has other light passed through it onto another larger piece of paper (like an overhead projector in school). The light that passes through the film reacts to chemicals on the paper to reproduce the image, but with the correct colors, and a larger size so you can view it nicely. (there are more details, but this is ELI5)
With digital cameras, the process is the same, but instead of light hitting a photo-reactive film behind the camera lens, it hits a device called an image sensor (https://puu.sh/F7PUY/63f7b62ee1.png).
This sensor is an array of photosites (one site for each pixel in the resulting image) which reacts to light photons by generating a tiny electrical charge. The brighter the ligh, the more photons are collected and a higher charge is generated. Different photosites will register different electrical charges and, once the shutter exposure period is over, each individual pixel photosite’s charge is then measured and turned into a digital value by a simple computer inside the camera’s electronics.
Then later those values are reassembled and converted into color pixels to display on whatever you’re viewing the image on (your computer screen, or phone screen, for example).
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