Using a three-dimensional hydrodynamical model of the solar atmosphere, we calculated profiles of the Fe I lambda 639.361 nm and Fe II lambda 523.462 nm lines with consideration for deviations from the local thermodynamic equilibrium. We determined heights for intensity contrast reversal and for velocity sign reversal of convective elements. Both of these parameters depend strongly on the convective velocity and intensity measured in the continuum. The larger the parameters, the greater is the atmosphere altitude where the reversal takes place. We compared all the calculated relations with the observations obtained at the German Vacuum Tower Telescope in Izana (Tenerife, Spain). In our opinion, the 3D hydrodynamical model of the solar atmosphere satisfactorily describes all the main features of observed convective velocities and intensities.