This book (Practical Electron Microscopy and Database) is a reference for TEM and SEM students, operators, engineers, technicians, managers, and researchers.
 

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By changing the angle of illumination upon the TEM sample, the coherence of the electron beam can be varied. Figure 1709 shows the ratio of Fourier spectra taken from two calculated CTFs at different beam convergences (0.38 and 0.36 mrad). This figure indicates the non-constant effect of coherence (beam convergence angle) on CTF.

Figure 1709. The ratio of Fourier spectra taken from two calculated CTFs at different beam convergences. Adapted from [1]

[1] Peter D. Miller and J. Murray Gibson, Connecting small-angle diffraction with real-space images by quantitative transmission electron microscopy of amorphous thin-Þlms, Ultramicroscopy 74 (1998) 221-235.