A system for measuring temperature of at least two subjects (120-a, 120-b, 120-c) within a scene including a reference object, the reference object having an unknown emissivity and an ambient temperature, wherein the ambient temperature of the reference object is the scene ambient temperature, the system comprising: a visible spectrum camera configured to acquire images of the scene comprising (a) at least a Region of Interest, RoI (130-a, 130-b, 130-c), of each of the subjects, and (b) the reference object; a thermal image sensor configured to acquire images of the scene comprising (a) at least the RoI of each of the subjects, and (b) the reference object; and a processing circuitry configured to: obtain (a) a visible spectrum image captured by the visible spectrum camera, and (b) a thermal image captured by the thermal image sensor, and (c) an indication of the scene ambient temperature within the scene; register the visible spectrum image and the thermal image onto a common coordinate system; identify (a) RoI pixels, on the common coordinate system, of the RoIs of the subjects within the visible spectrum image, and (b) reference object pixels, on the common coordinate system, of the reference object within the visible spectrum image; determine (a) RoI temperatures of the RoIs of the subjects, by analyzing the identified RoI pixels on the thermal image, (b) a reference temperature by analyzing the reference object pixels on the thermal image, and (c) a parameter correlated to an emissivity of the reference object, based on the reference temperature and on the indication of the scene ambient temperature; and upon existence of a difference between the reference temperature and the indication of the scene ambient temperature, correct the RoI temperatures, based on the difference and utilizing the parameter, to compensate for the difference, giving rise to corrected RoI temperatures. a visible spectrum camera configured to acquire images of the scene comprising (a) at least a Region of Interest, RoI (130-a, 130-b, 130-c), of each of the subjects, and (b) the reference object; a thermal image sensor configured to acquire images of the scene comprising (a) at least the RoI of each of the subjects, and (b) the reference object; and a processing circuitry configured to: obtain (a) a visible spectrum image captured by the visible spectrum camera, and (b) a thermal image captured by the thermal image sensor, and (c) an indication of the scene ambient temperature within the scene; register the visible spectrum image and the thermal image onto a common coordinate system; identify (a) RoI pixels, on the common coordinate system, of the RoIs of the subjects within the visible spectrum image, and (b) reference object pixels, on the common coordinate system, of the reference object within the visible spectrum image; determine (a) RoI temperatures of the RoIs of the subjects, by analyzing the identified RoI pixels on the thermal image, (b) a reference temperature by analyzing the reference object pixels on the thermal image, and (c) a parameter correlated to an emissivity of the reference object, based on the reference temperature and on the indication of the scene ambient temperature; and upon existence of a difference between the reference temperature and the indication of the scene ambient temperature, correct the RoI temperatures, based on the difference and utilizing the parameter, to compensate for the difference, giving rise to corrected RoI temperatures. obtain (a) a visible spectrum image captured by the visible spectrum camera, and (b) a thermal image captured by the thermal image sensor, and (c) an indication of the scene ambient temperature within the scene; register the visible spectrum image and the thermal image onto a common coordinate system; identify (a) RoI pixels, on the common coordinate system, of the RoIs of the subjects within the visible spectrum image, and (b) reference object pixels, on the common coordinate system, of the reference object within the visible spectrum image; determine (a) RoI temperatures of the RoIs of the subjects, by analyzing the identified RoI pixels on the thermal image, (b) a reference temperature by analyzing the reference object pixels on the thermal image, and (c) a parameter correlated to an emissivity of the reference object, based on the reference temperature and on the indication of the scene ambient temperature; and upon existence of a difference between the reference temperature and the indication of the scene ambient temperature, correct the RoI temperatures, based on the difference and utilizing the parameter, to compensate for the difference, giving rise to corrected RoI temperatures.