This mod just simply make the indoor lights brighter. I changed the LightRigScale in the data file Renderer.GlobalLightSettings ( 545AC67A-00B2600F-DEAD4915C9C6C0D8 in clientfullbuild9.package).
You can adjust the brightness urself in game, or make it even higher.
9/7/ Updated the version that slightly increased the environmental lighting. The default brightness is lowered by 40%, but still much brighter than vanilla game.
For some of user reported that the brightness went back, it's caused by loading(include loading, leaving lot, entering CAS etc.). The brightness will be automatically set back to default when you try to modify the brightness again after loading.
This issue also appeared in vanilla game without modding, it's not caused by this mod. Hope some day EA will fix this problem.
Here I recommend you, once you have finished modifying your brightness, then ignore those lamps at all!
Default brightness level
Adjusted on your own
s4pe by kuree https://github.com/Sims4Group/Sims4Tools/releases
s4 data file tool by velocitygrass http://modthesims.info/showthread.php?t=531876