It freezes a moment in time and records it to film or a digital file. But how?
Its components are a mechanical recreation of the human eye.
The eye has an iris, retina and eyelid. Respectively, the camera has a lens, film and shutter. Together these control the amount of light, sensitivity to light, and duration of exposure to light. When all three parts work together, they create the optimal image.
The iris of your eye is light’s gateway to the retina. It adjusts to let in more or less light depending on brightness. On a bright day, the iris becomes very small, allowing less light to pass through. In a dimly lit room, the iris opens very wide. Ditto for the camera lens. When you’re taking a picture at dinner in a restaurant, you have to open the lens very wide to capture more light.
Think of the retina as the film inside your eye. Film has a fixed sensitivity to light. It needs enough light to register an image, but too much will over expose the film and ruin the picture. Your eye needs a certain amount of light to make sure you don’t stub your toe in the dark, but too much will be blinding.
Eyelids control how long light passes through to the iris (lens) and onto your retina (film).
It protects the retina from being overexposed and blinding you. The shutter of a camera works
in the same fashion. It helps control the amount of light that is absorbed by the lens,
which, in turn, passes light through to the film. If both the shutter and lens filter
the proper amount of light, the film will be perfectly exposed, providing the optimal photograph.