Radiography is a method of nondestructive testing that utilizes radiation to penetrate an object and record images. The images can be recorded on a variety of different devices such as film or photosensitive paper. The result is a two dimensional projection of the part onto the film, producing a latent image of varying densities according to the amount of radiation reaching each area. It is known as a radiograph, as distinct from a photograph produced by light. Because film is cumulative (becoming greater by successive additions) in its response, relatively weak radiation can be detected by prolonging the exposure until the film can record an image, which will be visible after development. The radiograph is examined as a negative, without printing as a positive as in photography.