In multiwavelength pyrometry it is very difficult to represent the wavelength variation of emissivity so that a ‘‘correct’’ blackbody temperatureT0is obtained. On the other hand, use ofTr’s, the radiance temperature, permits the calculation of the blackbody temperatureT0. In all cases studied up to now, in the wavelength range 0.4–4 &mgr;m, we have a linear relationship betweenTrandL, the wavelength,Tr=Tlin−hL, whereTlinis the calculated blackbody temperature.