I run Ubuntu 12.04 on my netbook (Acer Aspire One D255E) and I have the following problem with the brightness settings: If I want to adjust the brightness with the fn-key, I can only change between three brightness steps, but my netbook has nine brightness steps.
If I adjust the brightness in the system settings, it works fine and I can choose between nine steps, so I know they are there. They are just jumped, when I use the fn-keys. The funny thing: If I click the fn-key like crazy, I can get to the steps between, too. Does anybody have an idea, what the problem might be?