Instagram users 80+M photos every day. Snapchat users share 8,796 photos every second. Facebook users post 350 million photos per day, and 4,501 per second. Every two minutes, humans take more photos than ever existed in total 150 years ago. But what essentially is a photo? In order to answer this question, let’s try to understand how cameras work.
How film camera work?
This old-style camera makes photos with a film, a thin flexible strip of plastic or other material coated with light-sensitive emulsion. The emulsion is made of silver halide crystals, that will capture the image when exposed to light. When you press a button, your camera activates a mechanism called the shutter, which makes a hole (the aperture) open for a fraction of a second at the front of the camera, allowing light to enter through the lens. When the light passes through to the film, the silver halide crystals turn into silver ions. The density of the silver ions, compared with the remaining silver halide, represents the intensity of the light in that area of the picture. Thus, the image is stored on the film until processed.
How digital camera work?
Digital cameras work in a similar but completely different way. When you press the button on your digital camera, an aperture opens and lets the light stream in through the lens. The light is then captured and turned into electrical signals by a piece of electronic called a charge-coupled device (CCD). The CCD breaks it up into millions of pixels, measures the color and brightness of each pixel and stores it as a number. Ultimately, a digital photo is a long string of numbers describing the exact details of each pixel it contains. Once a picture is stored in numeric form, it can be shared between different gadgets, edited on the laptop or uploaded online. “Digital” is a kind of language that all electronic gadgets “speak” today.
Now, stop here and think about it for a while. Each photograph is effectively a captured document of an evanescent state of light. That to me is the most fascinating fact about the photography.
Featured photo: Nobuyoshi Araki, Paradise 2, 2013