Using dm or refmac after SHARP

[Kevin Cowtan <cowtan@yorvic.york.ac.uk>]

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Just a reminder, because I keep getting mails where this has caused
problems (I'll add it to the dm doc too):

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SHARP is probably the best source of phasing for density modification.
However, if you wish to run dm after SHARP you should first turn off
the Solomon option.

Solomon produces excellent maps, and so often having run SHARP and
Solomon you will not want to use dm at all. However, Solomon produces
badly overestimated FOM's (typically 0.9 - 0.95), which while they do
not damage the maps, effectively cripple any further density
modification (or for that matter any phased maximum-likelihood
refinement calculation).

(Since the FOM is based on an estimate of the error in the phases, a
high FOM implies that the phases are correct and therefore should not
be modified by any subsequent procedure. Thus further density
modification will not change the maps, and ML-refinement will be badly
biased by the erros in the starting phases.)

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Another option is to run 'dm' then 'Solomon', since 'dm' works very
hard to keep the FOMs reasonable. 'dm' phases and FOMs may also be
used in refmac, along with the 'blur' option to remove the moderate
amount of overestimation which still occurs.

Kevin