  It is shown that spatial correlation functions measured for correlated photon
pairs at the single-photon level correspond to speckle patterns visible at high
intensities. This correspondence is observed for the first time in one
experimental setup by using different acquisition modes of an intensified CCD
camera in low and high intensity regimes. The behavior of intensity auto- and
cross-correlation functions in dependence on pump-beam parameters including
power and transverse profile is investigated.
