Emissivity is the ability of an object to emit or absorb energy. Perfect emitters have an emissivity of 1, emitting 100% of incident energy. An object with an emissivity of 0.8 will absorb 80% and reflect 20% of the incident energy. Emissivity may vary with temperature and spectral response (wavelength). Infrared thermometers will have difficulty taking accurate temperature measurements of shiny metal surfaces unless they can adjust for emissivity.