  A description is provided of the performance of the CMS detector for photon
reconstruction and identification in proton-proton collisions at a
centre-of-mass energy of 8 TeV at the CERN LHC. Details are given on the
reconstruction of photons from energy deposits in the electromagnetic
calorimeter (ECAL) and the extraction of photon energy estimates. The
reconstruction of electron tracks from photons that convert to electrons in the
CMS tracker is also described, as is the optimization of the photon energy
reconstruction and its accurate modelling in simulation, in the analysis of the
Higgs boson decay into two photons. In the barrel section of the ECAL, an
energy resolution of about 1% is achieved for unconverted or late-converting
photons from H to gamma gamma decays. Different photon identification methods
are discussed and their corresponding selection efficiencies in data are
compared with those found in simulated events.
