Holographic interferometry has been applied, in the presence of strong beam deflection effects, to the study of the coupling of gas-gas radiative transfer and free convection in a 0.9 m(3), isothermal, gastight cavity containing an isothermal plate of finite thickness and filled with N-2 or CO2. The cavity is heated in the range 290-650 K with the plate at a higher temperature. The focus of this paper is on the validation of an original experimental procedure for the determination of thermal fields in the region close to the plate. Experimental results agree both with independent experimental results using a laser beam deflection technique and, in case of pure free convection. with classical bibliography results related to a vertical wall, It has been shown that gas-gas radiative transfer significantly modifies the temperature field corresponding to free convection and increases the local heat transfer coefficient.