The Basics of a Camera

The word “camera” comes from the Latin term camera obscura, or “dark chamber”, which refers to the common feature of all cameras: they consist of a closed chamber in which to capture light. The desire to capture light and record it onto a somewhat permanent medium goes all the way back to the first physicists’ wishing to understand how the eye captures images of the outside world. For as long as the idea has been around, the camera has been thought of as a kind of mirror of the human eye and human vision.

Like the eye, a camera consists of an opening, or aperture, into which light can pass, and some kind of medium to receive the image. In the case of the eye, that medium is the optic nerve. Over the years, many mediums have been tried in cameras, from metal plates to electronic sensors. While each subsequent technological advance brought its own advantages, each is also in some sense “imperfect” as a reflection of reality. There are various reasons for this. Some mediums are more sensitive to certain spectra of light than others and thus leave out crucial bits of light information in their images. Camera images can be blurred by motion or improper focus. Even in a focused picture, foregrounding an image makes it appear proportionately larger, though in reality it has not grown at all. Finally, no camera can capture everything in a given shot, so what you see is really only a “slice” of reality, and not a one-to-one representation of everything there is. For these reasons, photography is thought of as the “art of making pictures” instead of a mere recording of reality. While cameras have been made that can match and even surpass the eye’s ability to collect light, they all share this feature of interpreting and in some sense changing the reality they represent.

Many cameras employ a lens to bend light before it reaches the aperture. The purpose of a lens is to collect light from a larger area. For this same reason, our eye also employs a lens, in form of the curvature of its outer membrane. The lens on a camera is made of curved glass. On some cameras, more than one lens is employed to adjust the angle of the light or to increase the distance at which the camera can achieve a clear picture. Lenses also help with focusing a picture, by directing light towards the aperture in concentrated rays. In autofocus cameras, such as disposable film cameras, the lens is constructed such as to offer focused pictures in a set range of distances, but cannot be adjusted. More advanced cameras, such as single lens reflex-type cameras, have adjustable lenses, usually by a moveable ring around the lens casing, to achieve clear images at remarkable ranges.

Besides focus, the other main factor determining how a photograph will come out is the amount of available light. Because all cameras depend in some way on physical effects of light on the photographic medium, controlling the amount of light and the length of exposure of the medium to the light are crucial functions of the camera. The amount of light that can enter a camera is limited by the size of the aperture, while the length of exposure is controlled by the shutter. On many cameras, the shutter speed can be adjusted to allow more light in darker environments, and less light in brighter ones. Some cameras have light sensors to automatically adjust shutter speed, or indicate to the photographer which speed is recommended.

With these basic controls, the photographer is in charge of the process of “making pictures”: of choosing compositions, focusing on subject matter, and creating photographic effects such as controlled blurring or over or under-exposing shots. Photographers can construct narratives by making sequential shots of an event. Some photographers experiment with preparing the scenes or subject matter they are photographing in order to achieve even more creative control of their images.