What is the Ambient Light Sensor feature on a laptop, and how do I adjust the settings?

Ambient Light Sensor Functionality (ALS)
 

When a Dell legacy laptop is equipped with an Ambient Light Sensor, it has a small square window that is located at the bottom edge of the LCD panel (Figure 1).

For information about how to manually change the screen brightness on a Dell laptop, see Dell Knowledge Base article How to Change the Video Settings or Improve Text in Windows.

Figure 1: Ambient Light Sensor Location

The ALS increases the brightness of the LCD panel when used in a brightly lit area and dims the display when used in darker areas. By design, brightness changes are made gradually to prevent flickering and may not be easily noticed.

The ALS is disabled by default when the computer is shipped from the factory, but can be enabled by using:

• The Fn + Left arrow keyboard shortcut
• The Dell QuickSet utility
• The System Setup (BIOS)

Enable or Disable the Ambient Light Sensor (ALS) Using the Keyboard
 

To enable or disable the Ambient Light Sensor (ALS) using the keyboard: 

• Press and hold the Fn key, and press the Left Arrow key to enable or disable ALS.
• Press and hold the Fn key, and press either the Up Arrow key or the Down Arrow key to disable ALS and set the LCD brightness manually. Pressing the Up Arrow key brightens the display, and pressing the Down Arrow key dims the display.

Enable or Disable the Ambient Light Sensor (ALS) Using the Quickset Tool
 

When changing the status of the Ambient Light Sensor (ALS) using the keyboard shortcuts, the Dell™ Quickset utility opens messages indicating if the ALS has been disabled.

To configure the ALS using the Dell Quickset utility, perform the following steps:

1. Double-click the Quickset icon  in the system tray.
    
2. On the Dell Quickset window, click the Panel Brightness link.
   The Quickset LCD Panel Brightness Control windows opens (Figure 3).
   
   
   Figure 3: ALS operating range setting. (English only)
    
3. Select a radio button to choose from the following:
   • Enable Ambient Light Sensor: Enables the ALS. The minimum and maximum brightness range can be set using the slider controls.
   • Enable Ambient Light Sensor to optimize BATTERY SAVINGS: Enables the ALS using a preset brightness range to enhance battery performance. The maximum brightness cannot be increased beyond the default setting.
   • Disable the Ambient Light Sensor: Disables the ALS and the brightness range slider. The LCD panel brightness must be manually set using keyboard shortcuts or the System Setup (BIOS).

Enable or Disable the Ambient Light Sensor (ALS) Using the System Setup (BIOS)

To enable or disable the Ambient Light Sensor (ALS) using the System Setup (BIOS):

1. Reboot the computer.
    
2. Press F2 at the Dell splash screen to enter the BIOS (System Setup).
    
3. Use the Down Arrow key to highlight Video, then press Right Arrow to expand the menu.
    
4. Press Down Arrow to highlight Ambient Light Sensor, then press Enter.
    
5. Press Right Arrow to select Off or Enabled, then press Enter.
    
6. Press F10 to Save and Exit.
    
7. When prompted to Save changes and exit now, press Enter.
   
   Your computer now restarts.