What I am saying is, if you display the DELTA_SV propcase on my S95 it is always zero, it never changes.
Does it change on your camera ?
It may only be valid when get_shooting() is true (shooting_in_progress()!=0). Yes, DELTA_SV and SV procases both hold data, and seem to return what you stored in them. That's why this works to set the SV:
set_prop(pDELTA_SV,sv-get_prop(pSV)+get_prop(pDELTA_SV))
I'm saying that having multiple functions to set sv96, tv96, and av96 using there linear equivalents is confusing. You can only change exposure with an APEX96 value, so why not have a conversion function separate from the exposure function.