It's common for laptops to have a lower brightness when working on battery, to have a longer battery lif. But they also have an option (a function key or such) to adjust the brightness to your liking.
So your course of action should be to read the user manual, I think.
Kees
Bought a new Dell XPS 15 laptop, 1 week back.
Config : Intel Core i5, Nvidia GeForece GT 540M ( Optimus ) with Intel HD onboard Graphic, 8 GB RAM
The issue is that the color of the screen looks unreal, like the color of icons fade and look like 256 bit color mode and whitish and faded.
The main point is that the issue only occurs when the system is operating on battery. Is the issue with Optimus Technology ?
I have the latest drivers, Would should be my course of action now ?

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic