[conspire] On Intel Core i3 notebook, display brightness setting ignored

roger at rogerchrisman.com roger at rogerchrisman.com
Sat Dec 18 23:12:17 PST 2010


My notebook's display is not honouring the brightness settings in
Linux. The display seems to ignore the settings and is a bit too
bright for comfort.

The graphics chip is integrated Intel and the display is Active Matrix
TFT Color LCD. More specs are below my signature.

I bought this nice Acer Aspire 5742-7645 notebook computer at Costco
in Mountain View a few days ago. I installed Xubuntu 10.10 amd64 and
Ubuntu 10.10 amd64 on it (and it also has its original Windows 7
64bit). It has a Broadcom wireless card--wireless didn't work when
booted into either the above desktop-install disks. So I chose "[x]
install third-party software" during both Linux installs and that got
the Broadcom wireless working.

So far everything I have tested works except _display brightness
settings_. In Windows 7 it works, the Fn+arrow kets adjusts display
brightness as expected. But in Xubuntu and Ubuntu the display seems to
be at full brightness and Fn+arrow keys does _not_ change it. It does
something, I think a setting is adjusted somewhere, but the display
brightness remains unchanged and is a bit too bright. I have been
learning as I study this but haven't solved it yet. Here's what I've

The Fn+arrow keys set something somewhere: after using them to set the
display to its lowest setting, xbacklight -get shows me 0.000000:

roger at a:~$ xbacklight -get

And after using Fn+arrow keys to set display to full bright,
xbacklight -get shows me 100.000000:

roger at a:~$ xbacklight -get

If I set to middle brightness with Fn+arrow keys, xbacklight -get
shows me 55.555556:

roger at a:~$ xbacklight -get

All the while the display brightness however remains unchanged--it
remains at what appears to be full brightness.

I read on Wikipedia that hal is deprecated and that Ubuntu, as of
v10.4, uses udev instead.

I thought to use udev to somehow set display brightness. But when I
found with xbacklight -get that settings seem to be happening already,
somewhere, and yet are not effecting display brightness, I decided it
is time to ask on Conspire. In any case I don't know how to adjust
things with udev, not the least display brightness. Is it easy?

The graphics chip is integrated Intel and the display is Active Matrix
TFT Color LCD. More specs are below my signature.

Any ideas what is preventing my display from honouring the brightness
settings in Linux?

Roger, Palo Alto
Acer Aspire 5742-7645 notebook
Xubuntu 10.10 amd64 (and Ubuntu 10.10 amd64, and Windows 7 64bit)
Broadcom wireless card, working
specs from
(site does not show my exact Costco model unfortunately)
==Display & Graphics==
Screen Size 	15.6"
Display Screen Type 	Active Matrix TFT Color LCD
Display Screen Technology 	CineCrystal
Aspect Ratio 	16:9
Screen Mode 	WXGA
Backlight Technology 	LED 	(I think, not sure)
HDCP Support 	Yes
Display Resolution 	1366 x 768
Color Support 	16.7 Million Colors
Graphics Controller Manufacturer 	Intel
Graphics Controller Model 	Graphic Media Accelerator HD
Graphics Memory Technology 	DDR3 SDRAM
Graphics Memory Accessibility 	Shared
==Processor & Chipset==
Processor Manufacturer 	Intel
Processor Type 	Core i3
Processor Model  	i3-370M
Processor Speed 	2.40 GHz
Processor Core 	Dual-core
Cache 	3 MB
64-bit Processing 	Yes
Hyper-Threading 	Yes
Chipset Manufacturer 	Intel 	
Chipset Model 	HM55 Express

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