  We present a way to account for coherence length effects in a semi-classical
transport model. This allows us to describe photo- and electroproduction at
large nuclei (A>12) and high energies using a realistic coupled channel
description of the final state interactions that goes far beyond simple Glauber
theory. We show that the purely absorptive treatment of the final state
interactions as usually done in simple Glauber theory might lead to wrong
estimates of color transparency and formation time effects in particle
production. As an example we discuss exclusive rho^0 photoproduction on Pb at a
photon energy of 7 GeV as well as K^+ and K^- production on C and Pb in the
photon energy range 1-7 GeV.
