  The reduced cross section for exclusive ($e,e'p$) reactions has been studied
in DWIA for the example of the nucleus $^{16}$O using a spectral function
containing effects of correlations. The spectral function is evaluated directly
for the finite nucleus starting from a realistic nucleon-nucleon interaction
within the framework of the Green's function approach. The emphasis is focused
on the correlations induced by excitation modes at low energies described
within a model-space of shell-model configurations including states up to the
$sdg$ shell. Cross sections for the $p$-wave quasi-hole transitions at low
missing energies are presented and compared with the most recent experimental
data. In the case of the so-called perpendicular kinematics the reduced cross
section derived in DWIA shows an enhancement at high missing momenta as
compared to the PWIA result. Furthermore the cross sections for the $s$- and
$d$-wave quasi-hole transitions are presented and compared to available data at
low missing momenta. Also in these cases, which cannot be described in a model
without correlations, a good agreement with the experiment is obtained.
