Dual photography

Dual photography is a photographic technique that uses Helmholtz reciprocity to capture the light field of all light paths from a structured illumination source to a camera. Image processing software can then be used to reconstruct the scene as it would have been seen from the viewpoint of the projector.

It also represents the art of simultaneously taking two photographs (a dualphoto) of one scene, one front facing, the other in the same axis but backfacing at 180 degrees (as with popular smartphone apps like FrontBack or Duall Dualphoto).