Backgound information

Definition: Photography is the process, activity and art of creating still or moving pictures by recording radiation on a sensitive medium, such as a photographic film, or an electronic sensor or chip. The light patterns emitted from objects activate a sensitive chemical or electronic sensor during a timed exposure, usually through a photographic lens in a a camera that also stores the resulting information chemically or electronically (digitally).

Meaning: the actual word "photography" comes from the Greek φώς (phos) "light" + γραφίς (graphis) "stylus", "paintbrush" or γραφή (graphê) "representation by means of lines" or "drawing", together meaning "drawing with light" or painting with light. Using film, the products of photography have been called negatives and photographs, commonly shortened to photos or even pics.

The camera's functions. A camera is the image-forming device, and photographic film or an electronic image sensor is the sensing medium which captures the image. Recording media can be the film itself, or a digital electronic or magnetic memory card.

Photographers control the camera and lens to "expose" the light recording material to the required amount of light to form a "latent image" (on film) or "raw file" (in digital cameras) which, after processing, is converted to a usable image or photograph. The latest digital cameras replace film with an electronic sensor based on light-sensitive electronics such as charge-coupled device or complementary metal-oxide-semiconductor CMOS technology and electronics. Digital images are stored electronically, but can be reproduced on paper or film or slides.

A movie camera is a type of photographic camera which takes a rapid sequence of photographs on strips of film or digital code. This contrasts with a still camera, which captures a single snapshot at a time, the movie camera takes a continuous series of images, each called a "frame" or snapshot.

The movie effect is achieved through an intermittent mechanism, either mechanical or electronic. Frames are later played back in a movie projector at a specific speed, called the "frame rate" (number of frames per second) or through a computer. When viewing, a person's eyes and brain merge the separate pictures together to create the illusion of motion ie a "movie".

This process of obtaining a usable exposure must involve the use, manually or automatically, of controls to ensure the photograph has clear, sharp and well-illuminated images. Controls usually include but are not limited to the following items:

Camera focus is the adjustment to place the sharpest focus where it is desired on the subject matter. Camera aperture is the adjustment of the iris, measured as f-number, which controls the amount of light passing through the lens aperture. This aperture also has an effect on focus and depth of field - the smaller the opening aperture, the less light but the greater the depth of field - that is, the greater the range within which objects appear to be sharply in focus. Focal length divided by the f-number gives the actual aperture size in millimeters or inches.

Camera shutter speed is the adjustment of the speed of the shutter to control the amount of time during which the imaging medium is exposed to light for each exposure or frame. The shutter speed is used to control the amount of light striking the image plane; 'faster' shutter speeds decrease both the amount of light and the amount of image blurring from motion of the subject and/or camera equipment.