Electron beam flux estimates were measured for all selected area electron diffraction settings described in methods section 2.2. First, the microscope was configured for parallel illumination. A magnification was selected such that the parallel beam filled the active area of the flu screen or the active area of the camera sensor. Electron flux was estimated from counts in a gain-corrected image of the parallel beam acquired by the Apollo. The number of electrons measured per pixel was determined from raw counts using a conversion factor of 16 counts per electron, corresponding to the value assigned to each detected event in Apollo's firmware. These values were used to determine the flux as a function of spot size, corresponding to ~ 0.01, 0.03, and 0.045 e-/Å 2 /s for spot sizes 11, 10, and 9, respectively.