  The production of direct photons, not coming from hadron decays, at large
transverse momentum pT > 2 GeV/c in proton-proton collisions at the LHC, is an
interesting process to test the predictions of perturbative Quantum
Chromodynamics at the highest energies ever and to put constraints on the gluon
density in the proton. Furthermore, they provide a baseline reference for
quark-gluon-plasma studies in Pb-Pb collisions. We will present the
experimental capabilities of the ALICE electromagnetic calorimeter EMCal to
reconstruct the direct and isolated photon spectra in p-p and Pb-Pb collisions.
