  We derive the redshift and the angular diameter distance in rotationless dust
universes which are statistically homogeneous and isotropic, but have otherwise
arbitrary geometry. The calculation from first principles shows that the
Dyer-Roeder approximation does not correctly describe the effect of clumping.
Instead, the redshift and the distance are determined by the average expansion
rate, the matter density today and the null geodesic shear. In particular, the
position of the CMB peaks is consistent with significant spatial curvature
provided the expansion history is sufficiently close to the spatially flat
LambdaCDM model.
