Como faço para definir o brilho da tela extral?
Você precisa instalar o Dell Display Manager .
Dell Display Manager
Dell Display Manager is a Microsoft Windows application used to manage a monitor or a group of monitors. It allows manual adjustment of the displayed image, assignment of automatic settings, energy management, window organization, image rotation, and other features on select Dell monitors. Once installed, Dell Display Manager runs each time the system starts and places its icon in the notification tray. Information about monitors connected to the system is available when hovering over the notification-tray icon.
Using the Quick Settings Dialog
Clicking Dell Display Manager's notification tray icon opens the Quick Settings dialog box. When more than one supported Dell monitors are connected to the computer, a specific target monitor can be selected using the menu. The Quick Settings dialog box allows you to easily adjust the brightness, contrast, resolution, window layout, and so on. It also allows you to enable automatic switching between preset modes or to select a preset mode manually.
Fonte Manual do usuário do Dell Display Manager :