  In this article we present a local hidden variables model for all experiments
involving photon pairs produced in parametric down conversion, based on the
Wigner representation of the radiation field. A modification of the standard
quantum theory of detection is made in order to give a local realist
explanation of the counting rates in photodetectors. This model involves the
existence of a real zeropoint field, such that the vacumm level of radiation
lies below the threshold of the detectors.
