[en] The S-matrix electrodynamics method is used for the analysis of processes with 1/2 spin particles. This method allows one to calculate the soft (real and virtual) photon effects without perturbation theory approximation. The following results have been obtained. The terms of order k^-1, lnk, k⁰, kln²k are found in the bremsstrahlung matrix element, where k is photon energy. They are expressed through the matrix element of the process without emission and through static electromagnetic characteristics of particles (charge and magnetic moment). A threshold theorem has been derived for the Compton scattering on a particle with spin 1/2 up to the terms of order k²lnk. For the scattering amplitude of 1/2 spin charged particles we obtained two terms O(tsup(-1))+O(tsup(-1/2)) in the expansion over the momentum transfer squared t. The second term gives a correction for the Rutherford formula for cross section. The results obtained are essentially nontrivial consequencies of the gauge invariance. They are valid in all orders in coupling constant and in principle tolerable for an experimental test