Power spectra of a series of high resolution electron microscope image
s of a thin foil of crystalline silicon are compared with theoretical
predictions based on the standard theory for scattering and imaging of
electrons. The differences between theoretical and experimental power
spectra appear to be due to inexact knowledge of experimental paramet
ers rather than limitations of the theory. Examination of a number of
theoretical power spectra leads to an estimate of the optical paramete
rs of the microscope although not with the same precision that can be
achieved using an amorphous region of the specimen.