Fig. 3.

CTF fitted in the mean power spectrum of tilt series. The mean of rotationally averaged, background subtracted power spectra of all images of a tilt series were calculated (black lines). A CTF curve (dotted red line) was fitted using least square deviation methods. (A) Example from a tilt series of carbon film. The mean defocus value of the series is 3.5 μm. (B) Example from a cryo-tilt series of PRD1. The mean defocus value is 4 μm. The y axis in (B) is scaled up 20 times with respect to (A).