  Intensity correlation measurements form the basis of many experiments based
on spontaneous parametric down-conversion. In the most common situation, two
single-photon avalanche diodes and coincidence electronics are used in the
detection of the photon pairs, and the coincidence count distributions are
measured by making use of some scanning procedure. Here we analyse the
measurement of intensity correlations using multi-element detector arrays. By
considering the detector parameters such as the detection and noise
probabilities, we found that the mean number of detected photons that maximises
the visibility of the two photon correlations is approximately equal to the
mean number of noise events in the detector array. We provide expressions
predicting the strength of the measured intensity correlations as a function of
the detector parameters and on the mean number of detected photons. We
experimentally test our predictions by measuring far-field intensity
correlations of spontaneous parametric down-conversion with an electron
multiplying CCD camera, finding excellent agreement with the theoretical
analysis.
