  We demonstrate experimental generation of spatially-entangled photon-pairs by
spontaneous parametric down conversion (SPDC) using a partial spatially
coherent pump beam. By varying the spatial coherence of the pump, we show its
influence on the downconverted photon's spatial correlations and on their
degree of entanglement, in excellent agreement with theory. We then exploit
this property to produce pairs of photons with a specific degree of
entanglement by tailoring of the pump coherence length. This work thus unravels
the fundamental transfer of coherence occuring in SPDC processes, and provides
a simple experimental scheme to generate photon-pairs with a well-defined
degree of spatial entanglement, which may be useful for quantum communication
and information processing
