Defining Photography



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Photography is the art, science, and practice of creating durable images by recording light or other electromagnetic radiation, either chemically by means of a light-sensitive material such as photographic film, or electronically by means of an image sensor. Typically, a lens is used to focus the light reflected or emitted from objects into a real image on the light-sensitive surface inside a camera during a timed exposure. The result in an electronic image sensor is an electrical charge at each pixel, which is electronically processed and stored in a digital image file for subsequent display or processing.

The result in a photographic emulsion is an invisible latent image, which is later chemically developed into a visible image, either negative or positive depending on the purpose of the photographic material and the method of processing. A negative image on film is traditionally used to photographically create a positive image on a paper base, known as a print, either by using an enlarger or by contact printing.

The camera is the image-forming device, and photographic film or a silicon electronic image sensor is the sensing medium. The respective recording medium can be the film itself, or a digital electronic or magnetic memory.

Photographers control the camera and lens to “expose” the light recording material (such as film) to the required amount of light to form a “latent image” (on film) or RAW file (in digital cameras) which, after appropriate processing, is converted to a usable image. Digital cameras use an electronic image sensor based on light-sensitive electronics such as charge-coupled device (CCD) or complementary metal-oxide-semiconductor (CMOS) technology. The resulting digital image is stored electronically, but can be reproduced on paper or film.

The camera (or ‘camera obscura’) is a dark room or chamber from which, as far as possible, all light is excluded except the light that forms the image. The subject being photographed, however, must be illuminated. Cameras can range from small to very large, a whole room that is kept dark while the object to be photographed is in another room where it is properly illuminated. This was common for reproduction photography of flat copy when large film negatives were used (see Process camera).

A general principle known from the birth of photography is that the smaller the camera, the brighter the image. This meant that as soon as photographic materials became sensitive enough (fast enough) to take candid or what were called genre pictures, small detective cameras were used, some of them disguised as a tie pin that was really a lens, as a piece of luggage or even a pocket watch (the Ticka camera).

The movie camera is a type of photographic camera which takes a rapid sequence of photographs on strips of film. In contrast to a still camera, which captures a single snapshot at a time, the movie camera takes a series of images, each called a “frame”. This is accomplished through an intermittent mechanism. The frames are later played back in a movie projector at a specific speed, called the “frame rate” (number of frames per second). While viewing, a person’s eyes and brain merge the separate pictures together to create the illusion of motion.

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