Computer images that 'merge' two or more faces have recently become a staple of satirists, offering distorted portraits of the famous that alternately amuse and horrify us. But the technique used to create these composite images could have applications far beyond that of entertainment, however thought-provoking: soon forensic science, telecommunications and even medicine could well be using the method to refine their approaches.
The basic technique is not new - nor is the idea that it can be used for practical ends. In 1878 Francis Galton, an English explorer and scientist and a cousin of Charles Darwin, devised a photographic technique called composite photography, in which he superimposed images of two or more faces by means of multiple exposures. A similar effect can be achieved with a stereoscope and two photographs; the viewer sees a different face with each eye, but perceives one composite face.
For the technique to work, ...
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