Oh, I noticed similar topic already exists :
Single Monitor Restriction for a Dual Monitor Setup | f.lux forum

f.lux is not open source, but you may find the tools at http://psychtoolbox.org/ useful to your research. Good luck with your PhD work.

Oh wow, that's interesting that the range is limited.

What kind of tool do you use that measures so low?

O.K. cool. Thanks for the info.

Fantastic, happy to here that your working on it.
This isn't a Surface that I'm using, its a cheap Windows tablet and it does darken, but the darkest setting is still really bright at night in a dark room when I want to read when my wife is asleep. Thanks!