Video 2

Movie S2. Evolution of the CTF during a beam-induced phase shift (BIPS) image series with a 12-nm–thick amorphous carbon film at the back-focal plane heated to ∼60 °C. The series start on a fresh area of the film. The phase shift has an opposite sign to the Volta one, indicating beam-induced contamination and/or charging. The CTF extrema move outward, indicating phase retardation of the central beam with a zero appearing close to the FFT center early in the series. Acquisition parameters: beam current, 1 nA; beam diameter on the film, 25 nm; exposure time per frame, 2 s; defocus, 15-μm underfocus.