Photography is the art, science and practice of creating durable images by recording light or other electromagnetic radiation, either chemically by means of light-ensitive material such as photographic film, or electronically by means of 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 or 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 dependong on the purpose of the photographic material and the method of processing. A negative image on film is traditionally used to photographivcally create a positive image on a paper ase, known as a print, either by using an enlarger or by contact printing.