Sentence:  "The secret of all successful <WSD>double-exposure</WSD> photography may be expressed in one word—exactitude," said Georges Benoit, cameraman for Richard Walton Tully in "The Masquerader". 
Meaning of the word marked with <WSD> tags:  A photograph produced by exposing film or some other photosensitive surface to focused light twice, usually by opening and closing a camera shutter two times, thereby generating a picture consisting of two superimposed images.