Constraints on the Optical-IR extragalactic background from gamma-ray
  absorption studies
  Very high energy (VHE) gamma-rays from extragalactic sources, interacting by
gamma-gamma collisions with diffuse intergalactic radiation fields, provide an
alternative way to constrain the diffuse background light, completely
independent of direct measurements. The limits depend however on our knowledge
of the physics of the gamma-ray sources. After clarifying the interplay between
background light and VHE spectra, I summarize the extent and validity of the
obtainable limits, and where future improvements can be expected.
