Windows 8 brightness control for integrated displays
This topic provides information about brightness control for integrated displays on systems that are running Windows 8. It describes brightness-related user experiences and provides guidelines for system manufacturers to expose brightness control infrastructure to Windows. A checklist of guidelines for system manufacturers is provided. This information applies to Windows 8.
In this section
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Windows 8 improves the brightness user experience by providing users with new and intuitive brightness controls, combined with the familiarity of fine-grained controls on the desktop in Power Options and Windows Mobility Center. Users have quick and easy access to change screen brightness from the Settings charm. When pressing a brightness hardware button, an overlay gives the user immediate feedback on the brightness change. Additionally, on systems equipped with an Ambient Light Sensor (ALS), Windows automatically calculates the optimal brightness level, which users can override from PC Settings. |
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This section summarizes the platform requirements for supporting brightness control functionality on a Windows PC. |
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The configuration of the brightness control policies (settings) is performed through updates to the Windows power policy. For example, the Windows power policy includes the default display brightness level when the system is plugged in and when it is running on battery. This section provides a detailed list of power policy settings related to display and brightness. |
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Windows 8 cleanly separates brightness policies from the actual display brightness level. |
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Checklist of brightness control guidelines for system manufacturers |
System manufacturers should follow the guidelines that are described in this section when they develop Windows 8 platforms with integrated displays. |
Introduction
A well-designed and calibrated display is an important element to provide a fluid user experience on a Windows 8 PC. However, differences in display technology, outside lighting conditions, and user preferences can demand variances in display brightness levels. In addition, the display is often the greatest consumer of power in a portable computer. Therefore, a key determinant of a portable PC’s battery life is the power consumed by its display. To achieve an optimal end-user experience while not compromising battery life, Windows 8 provides a rich infrastructure to control and automatically adjust display brightness.
Windows 8 provides a range of new and intuitive UIs to control display brightness and other related settings through its new Windows Settings Charm interface. In addition, it displays a new overlay slider UI when brightness changes are invoked by keyboard hot keys. Other new features include support for hot key brightness changes based on the Human Interface Device (HID) protocol, enhanced support and algorithms for adaptive brightness adjustments based on changes in outside lighting conditions, as well as new support and requirements for smooth brightness transitions and scenario-based backlight power optimization. In addition, Windows 8 separates brightness policies from the actual display brightness. This allows users to modify or view the brightness policies irrespective of the actual brightness levels that are supported by the display (for further details, see How actual display brightness is determined).
In Windows 8, the primary mechanism by which a platform should expose its display brightness control functionality is the Windows Display Driver Model (WDDM) miniport device driver interface (DDI). The underlying brightness control infrastructure is configured by using a number of power policy settings. System manufacturers can customize a select subset of these settings based on the target platforms or display technologies.
System manufacturers and firmware developers should review this document for details on the Windows brightness control infrastructure, new user experiences, and power policy configuration details for display brightness. See Checklist of guidelines for system manufacturers.
Related topics
Keyboard Enhancements in Windows 8
Windows Hardware Certification Requirements
Integrating Ambient Light Sensors with Computers Running Windows 8
Advanced Configuration and Power Interface Specification