Calculations of photoionization cross sections for Na atoms and Na-like Fe15+ ions were carried out in the framework of relativistic multiconfiguration Dirac-Fock method. For Na atoms, comparisons were made with previous theoretical calculations and available experimental measurements and a good or at least reasonable agreement is found if the relativistic and relaxation effects are taken into account. It is shown that, for the outermost valence electrons of medium Fe15+ ions, the relativistic effects accounts for a prominent part in the photoionization process and orbital relaxation can be negligible; however it is not the same case for neutral Na atoms where the influence of orbital relaxations is significant but cross sections slightly depend on the relativistic effects.