The art, application, and practise of making long-lasting pictures by capturing light is referred to as photography. This may be accomplished chemically with the use of a light-sensitive substance such as photographic film, or electronically with the use of an image sensor.
In most cases, a lens is required to focus the light that is reflected or transmitted from objects onto the light-sensitive surface that is contained inside a camera during a timed exposure. When using an electronic image sensor, this results in the production of an electrical charge at each pixel. This charge is then electronically processed and saved in a digital picture file for display or processing at a later time. When using photographic emulsion, the final result is a latent picture that is invisible. This latent image is then "developed" using chemicals into a visible image, which may be either negative or positive, depending on the objective of the photographic material and the technique of processing. Through the use of an enlarger or contact printing, a positive image may be created photographically from a negative picture that has been captured on film.