Fig. 1.

Schematic showing information transfer for (A) continuous, (B) bidirectional and (C) dose-symmetric tilt-schemes. Tilts are shown from −60° to +60° in 3° increments for a total of 41 tilts. Grey values correspond to the information transfer at each tilt according to the color map shown on the left. The reduction of information transfer at high-tilts due to the increased apparent thickness of the sample is simulated by multiplication with the cosine of the tilt angle. The loss of high-resolution information due to accumulated electron dose is simulated by multiplication by low pass filters according to the measurements described in (Grant and Grigorieff, 2015) assuming constant exposure times. The dose-symmetric tilt-scheme shows optimized, near-symmetric information transfer. (D) Plot of mean signal transfer for different tilt-schemes: continuous (magenta); bidirectional starting at 0° (red); bidirectional starting at −21° (green); bidirectional starting at −21° in the case that the second branch is deleted before averaging to reduce impact of the jump-at-start problem (blue); dose-symmetric (black). Mean signal transfers are calculated as the mean of the signal transfer for all tilts within the tomogram.