The field in the database is a "Light Type" and is not a proportional ratio to its brightness.
These are the values that you want to go into that field:
https://github.com/EQEmu/Server/blob...t_source.h#L37
And those correlate these values:
https://github.com/EQEmu/Server/blob...t_source.h#L57
..using these comparisons:
https://github.com/EQEmu/Server/blob...source.cpp#L25
I have traded 'light' items to roaming mobs before and it does affect a change.