  We present a method to reconstruct the complete statistical mode structure
and optical losses of multimode conjugated optical fields using an
experimentally measured joint photon-number probability distribution. We
demonstrate that this method evaluates classical and non-classical properties
using a single measurement technique and is well-suited for quantum mesoscopic
state characterization. We obtain a nearly-perfect reconstruction of a field
comprised of up to 10 modes based on a minimal set of assumptions. To show the
utility of this method, we use it to reconstruct the mode structure of an
unknown bright parametric down-conversion source.
