The natural width of an X-ray peak is in oder of 1 eV in the range of interest, measured at FWHM. The detection process in EDS detector results in statistical uncertanty being introduced which distributes the X-ray information over a range of energies such that measured peak has a FWHM about two orders of magnitude greater than the nautral width. For example, a typical detector will produce a peak for Mn K alpha with a FWHM of 150 eV. The natural width of Mn K alpha is 2.3 eV. Consequently, a natural peak of 2.3 eV width having an amplitude of 1000 counts will be degraded to a peak of 150 eV width having 15 counts in the peak channel (assumed to be 10 eV in width). The peak width varies as function of peak energy.