How to increase the screen brightness control sensitivity?

Question

In Ubuntu 13.04, when I use the keyboard hotkeys to control my screen brightness, I only get 5 steps to go from the darkest to the brightest level, for a total of 6 levels.

However, I noticed a really strange behavior. If I click in any indicator, for example, in the clock so the calendar is displayed, while the menu (in this example, the calendar) is being displayed, I get 15 steps to go from the darkest to the brightest level, for a total of 16 levels, but I don't get the on-screen brightness notification though. This also occurs when the screen is locked. Maybe you, dear reader, haven't noticed this behavior so please try it.

This shows that somehow Ubuntu knows how to make use of the full brightness sensitivity, but it fails to do so under "normal" conditions (e.g. while a indicator menu is not being displayed, or the screen is not locked).

It also seems that the thing responsible for the on-screen brightness notification is doubling or tripling the brightness change on every step.

Having only 6 levels of brightness is very problematic because you can't adjust correctly the brightness according to the changing lighting conditions of your environment. In Windows in the same laptop, I get 16 levels of brightness as well.

How can I improve/increase the screen brightness sensitivity permanently?

Perhaps disabling the on-screen brightness notification? I could live without it if I get the brightness sensitivity back.

Answer 1

I have also noticed this issue on my Hp dv6t-7000 laptop with Intel HD 3000 graphics and a Nvidia GT 630m Optimus card. I eventually found a fix that worked from the Arch Linux wiki.

Basically my situation was that acpi_video0 was controlling the back-light, acpi_video0 is for ATI graphics. So, I added the following to the grub command line in /etc/default/grub acpi_osi="!Windows2012" acpi_backlight=vendor, so now it looks like this:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash i915.semaphores=1 acpi_osi="!Windows2012"  acpi_backlight=vendor"

Then ran:

sudo update-grub2 

A reboot and the sensitivity is fixed.

Hope this helps.