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entry variable: $sfmid -- statmask sigmoid threshold
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default: 0.0

This unmarked entry (second entry after "fmid"
entry) is only visible if middle-right "mask"
($statmaskampflag) is ticked.

The $sfmid entry defines the soft threshold for
masking the displayed "data" using a number in a
second "stat" file.  For example, the complex
amplitude or HDR response amplitude estimate
("data") can be masked with an estimated F-ratio
("stat").

This has the same usits as $sfthresh, but
performs a soft/fading threshold.

See the $fmid help for a lot more details.

N.B.: the units of this stat mask threshold
($sfmid) will *not* in general be the same as the
units of the data amplitude thresh ($fmid).

N.B.: the color scale bar and the color scale bar
limits are in amplitude units, not stat mask
units.

N.B. the color scale bar in the surface display
window is *not* stat-masked and so is only
affected by $fthresh, $fmid, and $fslope.
