LED power consumption not affected by brightness?

I have a Dell XPS 1330 LED and I was just wondering about the power consumption of my LED screen. I've always known that the brighter you have it while on battery, the more power you use. That's kinda obvious but just for the heck of it I started running tests to see how much power I was actually saving. I would usually use it on the darkest setting while on batter (yea, it's pretty hard to see during the day) but now I've been using it on the brightest setting which is obviously a heck of a huge difference. Yet it seems to be using the same wattage? On my power history I find no significant changes when using the brightest setting and my battery life even confirms this by giving me the same battery life as with the darkest setting. Can anyone confirm this or give insights on how this could be? Thanks

 

The difference between the lowest and brightest settings is less than 4W.. I measured it when on ac power, without the battery..

 

yeah, I have the LED screen as well, but just assumed that the screen brightness would make a big difference as far as battery life, nice find, this will definitely help...

 

What did you use to measure? Sometimes the reading aren't completely accurate. I usually get 2.5 hours on a normal run with brightness all the way down. I ran it from full charge till empty and it still gave me 2.5 hours... That's why I brought the question up. Any ideas?

 

Less than 4 W is a small amount of electricity.

 

4 W out of 10-20W is significant enough to make a difference. When tweaking laptop batteries, people rave about a savings of .7-1 W...

 

I measured current consumption(on the ac side), using a multimeter.. I could have used a wattmeter, but connecting it to the mains is a hassle.. Too many precautions..

 

If the wattage reported in RMClock is accurate, then there is less than 1 watt difference between max brightness and min. In addition, I noticed almost no difference between min and ~70% - 80% brightness

 

That's true.. the maximum diiference occurs between the screen at full brightness, and at 2 steps from maximum.. About 2.5W.. I measured the current consumption when in the the bios, to eliminate error due to processor loading, and other consumptions..

 

According to what I have noticed in rmclock, the difference between max and 3 steps down under idle conditions is ~2W
I actually prefer to keep the brightness down when in a properly lit room.