Does a thermal camera measure the true temperature of an object?
A thermal infrared camera measures a quantity called radiometric temperature by interpreting the infrared radiation emitted from the surface of objects within the scene. Each object is modeled as a blackbody with a unitary, spectrally flat emissivity profile that emits radiation only according to its temperature. Real objects do not have a unitary emissivity value and in fact, most real materials have spectrally varying emissivity profiles. Additionally, the thermal radiation from objects within the scene entering the camera is modified by the transmission properties of the intervening atmosphere. In order to convert the radiometric temperature measured by an infrared camera to the true thermodynamic temperature of an object, it is necessary to compensate for both the true material emissivity and atmospheric transmission properties.