A comparative estimation for inaccuracy in profile dependency of photon beams with the energy of 6 MeV has been considered using experimental data from ionization matrices and water phantom with ionization chambers. The regions of practicality for a matrix to test the photon 6 MeV beams quality under the clinical conditions were analyzed. The practical recommendations are given how to carry out the optimizing procedure of dosimetric experimental data during the analysis of therapeutic beam fields.