  We investigate the properties of cosmological distances in locally
inhomogeneous universes with pressureless matter and dark energy
(quintessence), with constant equation of state. We give exact solutions for
angular diameter distances in theempty beam approximation. In this hypothesis,
the distance-redshift equation is derived fron the multiple lens-plane theory.
The case of a flat universe is considered with particular attention. We show
how this general scheme makes distances degenerate with respect to w_X and the
smoothness parameters, alpha, accounting for the homogeneously distributed
fraction of energy of the i-components. We analyse how this degeneracy
influences the critical redshift where the angular diameter distance takes its
maximum, and put in evidence future prospects for measuring the smoothness
parameter of the pressureless matter, alpha_M.
