  Nearly two centuries ago Talbot first observed the fascinating effect whereby
light propagating through a periodic structure generates a `carpet' of image
revivals in the near field. Here we report the first observation of the spatial
Talbot effect for light interacting with periodic Bose-Einstein condensate
interference fringes. The Talbot effect can lead to dramatic loss of fringe
visibility in images, degrading precision interferometry, however we
demonstrate how the effect can also be used as a tool to enhance visibility, as
well as extend the useful focal range of matter wave detection systems by
orders of magnitude. We show that negative optical densities arise from
matter-wave induced lensing of detuned imaging light -- yielding
Talbot-enhanced single-shot interference visibility of >135% compared to the
ideal visibility for resonant light.
