  The photon is explored as an object to test the applications of QCD to the
perturbatively calculable collinear parton distributions. We investigate
analytic properties of DVCS amplitudes and related sum rules of generalized
parton distributions of the photon using as an input their earlier calculations
in the leading order. The relation of these GPDs to the quintessential
functions in the framework of the dual parametrization approach is also found.
