My laptop is Lenovo T400, and my OS is Ubuntu 10.10. I change the brightness of my screen by pressing the FN key and one of the two keys for increasing/decreasing brightness.
The brightness I feel comfortable is between two consecutive levels that are offered. So I wonder if it is possible to fine-tune the screen's brightness?
A somewhat overly technical answer, but you did ask "is it possible..."
Open Terminal and go to /sys/class/backlight, then into the backlight control's directory (the name varies, acpi_video0 in my laptop), then read the files max_brightness and actual_brightness. GNOME limits itself to 5 levels between zero and max, but the actual hardware usually has at least 10 levels. If the max_brightness file says "10" or more, a finer adjustment will be possible.
$ cd /sys/class/backlight
$ ls
acpi_video0@
$ cd acpi_video0
$ ls
actual_brightness device@ subsystem@
bl_power max_brightness type
brightness power/ uevent
$ cat max_brightness
10
You can write the desired level to a file named brightness in that directory, but in this example GNOME's own tool is used, which does not require root access.
$ pkexec /usr/sbin/gnome-power-backlight-helper --set-brightness 7
or in more recent versions of GNOME the path changed to:
$ pkexec /usr/lib/gnome-settings-daemon/gsd-backlight-helper --set-brightness 7
As Linker3000 said, there might be a GNOME Panel applet for controlling the brightness. Right-click the top panel and choose "Add".
The Fn+Key brightness levels are probably setup as a table in the machine's BIOS, but depending on your exact GUI setup (eg: Gnome, KDE etc..), there may be a plugin or widget that you can add to the desktop or status bar that adds a slider for screen brightness. I can't get in front of a Ubuntu machine with a GUI at the moment but I also believe there may be a brightness slider in some of the power management apps - maybe someone else can enlighten...
After installing pommed (sudo apt-get install pommed), I changed the step value to 0.3 (step = 0.3) in /etc/pommed.conf file. Restarted the computer and it is now working fine.
You can change the brightness with echo $VALUE | sudo tee /sys/class/backlight/intel_backlight/brightness where $VALUE is a number you want to try. Your permitted values are probably different from mine (0 to ~852). In the case of my Lenovo Thinkpad laptop, it simply says Invalid argument if a wrong value is used.
