We can monitor the electron diffraction pattern as we tilt the specimen. Note that tilting the specimen changes the focus in the case as shown in Figure 3912 (a). Therefore, the Eucentric height need to be re-adjusted. In the case shown in Figure 3912 (b), the focus is not changed. However, we normally are not so lucky to have such condition.
Figure 3912. (a) Specimen traverse induced by specimen tilting when there is a mismatch between optic axis and tilt axis, and (b) No specimen traverse induced by specimen tilting when there is no mismatch between optic axis and tilt axis.
In the case of TEM thin film, reflected relrods are formed. When the specimen or the electron beam is tilted, the spot position in the diffraction pattern moves because the Ewald sphere moves relative to the reciprocal lattice.