Mac: Where is control for screen dimming?

My Mac (iBook G4) screen seems to dim if I am away from it for even 5 minutes. This pisses me off.

I know that there is a control for “Put my computer to sleep” after so many minutes of idleness, but I have that set for 1/2 hour, and this does not seem to be related.

Can any of you Apple Dopers help me out?

On my PowerBook running Tiger, it is in the “Options” tab of the “Energy Saver” preferences panel.

It is a checkbox named “Automatically reduce the brightness of the display before display sleep.”

You can adjust the display sleep interval using the bottom slider in the “Sleep” tab.

OSX 10.4, System Preferences:
Energy Saver has separate controls for computer and display.
Desktop & Screen Saver has a “Start Screen Saver” control.