Similar to the diffraction contrast mechanism of TEM imaging, diffraction contrast has a substantial effect on the EELS intensity as well. Under strong diffraction conditions there is a significant loss of intensity so that any direct spatial interpretation from SIs (spectrum images) is almost impossible.
Diffraction effects can modulate the EELS intensity, resulting in overestimation of inelastic mean free path (IMFP, λ) of electrons by up to 25%.  Those effects can be minimized by selecting appropriate sample orientation.
To avoid strong diffraction effects, for instance, spectra for silicon (Si) crystals can be recorded with the electron beam slightly out of zone axes, e.g. tilt 6.7° away from the  and 2° from the  axis.
 Y. Y. Yang and R. F. Egerton, Micron 26, 1 (1995).