  Plane waves in noncommutative classical electrodynamics (NCED) have a
peculiar dispersion relation. We investigate the kinematical conditions on this
deformed "mass shell" which come from ultra high energy gamma rays and discuss
noncommutative dynamical effects on the gamma absorption by the infrared
background and on the intrinsic spectrum. Finally we note that in NCED there is
a strong correlation between the modified dispersion relation and the presence
of dynamical effects in electromagnetic phenomena such as in the case of the
synchrotron radiation. From this point of view, the limits on the typical
energy scale of the violation of Lorentz invariance obtained by deformed
dispersion relations and by assuming undeformed dynamical effects should be
taken with some caution.
