This parameter sets the lower extraction limit for the object.
A non-zero value for this parameter will over-ride the automatic object spatial-extent calculated by ECH_SPATIAL.
TUNE_OBJBLW can be used when the object extent and position relative to the order traces are well knwon. Typically, it will be used when the first of a set of similar frames has been manually extracted and automatation of the extraction of the remaining frames is required.
INITIAL SUGGESTED VALUE: 0.
Martin Clayton