Ubuntu – How to adjust the screen contrast

I have an Intel GMA 4500. I Googled for answers but nothing seemed to solve my problem.

Finally I came across this that says for acpi_osi=Linux, the brightness meter works in reverse, which was why my display started with a blank screen i.e. since it is reverse, max brightness = blank screen.

Following are a few interesting notes from the link:

1. Without i915.modeset=0 the backlight does appear to start in the off position. Hitting Fn-brighter once turns it back on. On my keyboard, brighter is Fn-left-arrow and dimmer is Fn-right-arrow, which is different than I usually see.

2. Starting with kernel modesetting gets me a graphical console that works fine until X tries to start.

3. X won't start with kernel modesetting, either automatically or from runlevel 3. X -configure fails. With nomodeset 1024x768 is the only available resolution once logged in to a session. Of note, kdm comes up at the correct resolution with nomodeset but once the X session starts it falls back to 1024x768.

4. acpi_osi=Linux is required for the back light keys to function. I see no lasting benefit to having turned it on and off as described in Comment #18 - still doesn't work with it off here.

5. Same symptoms booting from the F15 DVD. nomodeset option works at reduced resolution, black screen with default graphical installer.

So if your display starts with a blank screen, try decreasing the brightness to check if the screen appears. My display works fine now, but in reverse.