Fitting of arbitrary CTFs to the Fourier transform of RSV CA 2D
crystal. CTFs derived from arbitrary defocus values are fitted onto
FFT of RSV CA 2D crystal. Positions of calculated zero CTF are indicated by
green circles in the image, and clear misfit is observed when the wrong CTF
is fitted. Simulated CTF (red graph) was plotted based on the absolute
values (i.e., intensity profile mode) for the simplicity.