adjusting screen brightness

[Alimin Bijosono Oei]

>>Hi,
>>
>>I own a compaq presario 1500ap laptop and running FC1.
>>Is it possible to get the keyboard keys for adjusting screen brightness 
>>work? I managed to get other special keys work. Can the screen 
>>brightness itself be adjusted? I am not familiar with the underlying 
>>technical stuffs, is this something to do with X or anything else? 
>>Thanks for any help provided.
> 
> 
> [mwb at localhost ~]>> xgamma --help
> usage:  xgamma [-options]
>  
> where the available options are:
>     -display host:dpy       or -d
>     -quiet                  or -q
>     -screen                 or -s
>     -gamma f.f              Gamma Value
>     -rgamma f.f             Red Gamma Value
>     -ggamma f.f             Green Gamma Value
>     -bgamma f.f             Blue Gamma Value
>  
> If no gamma is specified, returns the current setting
> 
> For example:
> xgamma -gamma 1.5
> 

Xgamma won't allow me to change the gamma settings incrementally though 
. Is there any other way or tool that will allow me to do this?