Installation of the JET ITER-Like Wall (ILW)has brought on the need of a reliable protection system as too high a temperature of the plasma facing components (PFCs) can result in beryllium (Be) melting or thermal fatigue of tungsten (W). A proper temperature measurement relies on the knowledge of three different parameters of equal importance: the sensitivity of the camera sensor, the transmission factor of the optics used and the emissivity of the monitored PFCs. In this paper we first present the calibration process of a wide angle infrared (IR) camera, which has involved the capabilities of the remote handling for introducing a calibrated hot source into the JET vacuum vessel. Then, we describe how the PFCs equipped with embedded thermocouples have been used to assess the emissivity of both Be and W.