  We study nuclear shadowing for transverse and longitudinal photons. The
coherence length, which controls the onset of nuclear shadowing at small
Bjorken-x is longer for longitudinal than for transverse photons. The
light-cone Green function technique properly treats the finite coherence length
in all multiple scattering terms. This is especially important in the region
x>0.01, where most of the data exist. NMC data on shadowing in deep inelastic
scattering are well reproduced in this approach. We also incorporate
nonperturbative effects, in order to extrapolate this approach to small photon
virtualities Q^2, where perturbative QCD cannot be applied. This way, we
achieve a description of shadowing that is based only on quark and gluon
degrees of freedom, even at low Q^2.
