Abstract: A method of true temperature determination, including, (a) acquiring radiation emitted by an object at a plurality of wavelengths (50), (b) determining a characteristic of the acquired radiation which is based on a relationship between radiative emissions acquired at more than one wavelength (50), (c) determining a factor related to an error, using the characteristic (54) and calculating a current temperature of the object based on the correctional factor (56). Preferably, the factor is a vector of values indicating at least one emissivity value.