Picking particles from tilted pairs in Ximdisp. The specimen imaged in this example is Haliotis diversicolor hemocyanin, molecular weight 8 MDa (EMD-5585, EMD-5586; Zhang et al., 2013). Images were recorded on film at 200 keV. Ximdisp was used to pick particles manually from the left image (a) which was recorded with a specimen tilt angle of −5°. This was then transferred by Ximdisp to the middle image (b) which was recorded at a tilt angle of +5°. The positions of a few particles in the middle image were corrected manually and the shifts calculated by Ximdisp were used to correct the remaining particles automatically, as seen in the right image (c). A plot was obtained after alignment of both −5 and +5° sets of particles to the starting model and the tilt axis and angle describing the geometrical relationship between the two sets of particles calculated. The resulting tilt-pair plot is shown in Fig. 5(a).