Acer Aspire R7 with Haswell problem

I recently purchased this machine and love the design, but I seem to have to have a problem with the display. A few minutes after I unplug it, the screen seems to dim considerably but once in awhile the screen brightens back up then dims again. Sometimes, immediately after I unplug it, the screen instantly dims. When machine is plugged in, no problems, the screen is nice and bright. I can't find any power settings to deal with this. Is this natural with the new power saving haswell processor, or is this a problem with the machine?

 

It's a power-saving feature. You can set screen brightness for each power profile - separately for when the notebook is plugged and unplugged.
It's handled either by Windows (by default) or by Acer Power Management (or whatever it's called these days).

 

Found out, as I recently suspected, this model has a "ambient light sensor" which can change display brightness according to light in the room. Control panel--->power options--->choose power plan----->change plan settings---->change advanced power settings----> display-----> enable/disable adaptive brightness