  It is argued that the transparency of a medium for passage of a nucleon,
knocked-out in a semi-inclusive $(e,e'p)$ reaction and subsequently scattered
elastically, is not the same as the one measured in purely elastic scattering.
Expressions are given for the properly generalized transparency and those are
compared with recently proposed, alternative suggestions. Numerical results are
presented for selected nuclear targets and kinematic conditions, applying to
the Garino et al and the SLAC NE18 experiment.
