Radiograph vs. autoradiograph

To form an image by passing a beam of penetrating radiation (e.g. X-rays) through a specimen, and imprinting an image on film, is called a radiograph.

However, if the radiation comes from within the specimen to expose the film, the resulting image is said to be an autoradiograph. This process occurs when radioactive materials are accumulated in sufficient quantity in specimens that they may emit radiation upon decay to expose a nearby photographic emulsion.