The word photography comes from two ancient Greek words: photo, for "light," and graph, for "drawing." "Drawing with light" is a way of describing photography. When a photograph is made, light or some other form of radiant energy, such as X rays, is used to record a picture of an object or scene on a light-sensitive surface. Early photographs were called sun pictures, because sunlight itself was used to create the image. Mankind has been a maker of images at least since the cave paintings of some 20,000 years ago. With the invention of photography, a realistic image that would have taken a skilled artist hours or even days to draw could be recorded in exact detail within a fraction of a second.
Photographs are used extensively by newspapers, magazines, books, and television to convey information and advertise products and services. Practical applications of photography are found in nearly every human endeavor from astronomy to medical diagnosis to industrial quality control. Photography extends human vision into the realm of objects that are invisible because they are too small or too distant, or events that occur too rapidly for the naked eye to detect. A camera can be used in locations too dangerous for humans. Photographs can also be objects of art that explore the human condition and provide aesthetic pleasure. For millions of people, photography is a satisfying hobby or a rewarding career.