It is often desirable to control the scale of the calculated structure factors. The following applies only if IMOD .ne. 0. Inclusion of F000 will result in imposing non-negativity of electron density everywhere in the map prior to inversion, provided SC is reasonably well known. Intelligent use of this parameter would then require knowledge of the input map values prior to running the job. This is equivalent to imposing non-negativity, followed by one cycle through the tangent formula.
Phases can therefore be tangent formula refined or extended.