As a consequence of our previous study of equivalent wavelength variations, the so called equivalence relationship between absorbers allows a ready calculation of the influence coefficients of any absorbing element simply from the knowledge of the situation with one particular element. This simple procedure is discussed and then illustrated using the case of iron fluorescence as an example. It is considered particularly advantageous when practising accurate experimental calibration because it yields effective influence coefficients, i.e. that coefficient variation, as well as the particular geometry and spectral intensity distribution of the equipment being used are automatically accounted for. In addition, this method is liable to save much time and notably simplify the requirements for standards.