the auto brightness sensor keeps changing my screen brightness and it's annoying.

Diagnosis

The erratic shifting in screen luminosity on your BenQ EW3270U is caused by the B.I.+ (Brightness Intelligence Plus) system. This is a hardware-integrated light sensor located in the bottom bezel of the monitor that constantly samples the ambient light levels of your room. When the sensor detects a change—such as a cloud passing over a window, a desk lamp being turned on, or even a shadow cast by your own body—it automatically adjusts the backlight intensity to maintain a perceived contrast ratio. This creates a "hunting" effect where the screen brightness fluctuates visibly and distractingly, especially in environments with mixed lighting (e.g., artificial light combined with natural daylight). To confirm this is the cause, place your hand directly over the sensor area at the bottom of the bezel; if the screen brightness immediately shifts, the B.I.+ system is the culprit. This is separate from the "Brightness Stabilizer" feature, which manages gamma and shadow detail rather than overall backlight intensity.

How to Fix It

To completely disable the automatic brightness adjustments and regain manual control over your luminance, follow these exact steps using the OSD (On-Screen Display) joystick/buttons:

1. Press the Menu button (located on the rear or bottom of the monitor) to bring up the main settings dashboard.
2. Navigate to the System menu. This is often grouped separately from the Picture settings in the EW3270U firmware.
3. Locate the B.I.+ option. You will see it is likely set to "On" or a specific profile (like "Office" or "WebCT").
4. Toggle the B.I.+ setting to Off. Once disabled, the sensor will stop polling the room light, and the screen will stop fluctuating.
5. Now, navigate to the Picture menu.
6. Select Brightness and use the directional controls to set a static percentage (e.g., 50% for indoor use, 80% for bright rooms).
7. Exit the menu by pressing the Exit or Menu button again to save the changes.

If That Didn't Work

• Check for HDR Override: If you have HDR enabled in Windows 10/11 (Settings > System > Display > Use HDR), the monitor may ignore manual brightness settings and fluctuate based on the HDR metadata of the content you are watching. Disable "HDR" in Windows to see if the brightness stabilizes.
• Disable Dynamic Contrast/DCR: In the OSD Picture menu, check if DCR (Dynamic Contrast Ratio) is enabled. DCR adjusts brightness based on the image on the screen (dark scenes get dimmer, bright scenes get brighter), which can be mistaken for the B.I.+ sensor. Set DCR to Off.
• Update Firmware: If the B.I.+ setting refuses to stay "Off" after a reboot, you may have a firmware glitch. Check the BenQ support site for the latest firmware update specifically for the EW3270U to resolve OSD persistence issues.
• Physical Sensor Obstruction: If you want to keep B.I.+ on but stop it from reacting to a specific light source, apply a small piece of neutral density filter or a semi-transparent tape over the sensor to dampen its sensitivity.

Heads Up

• Eye Strain: When disabling B.I.+, remember to manually lower your brightness at night. A static 100% brightness in a dark room can lead to significant eye fatigue and headaches.
• Color Accuracy: B.I.+ can slightly shift the white balance as it adjusts brightness. For color-critical work (photo editing, grading), always keep B.I.+ and DCR turned off to ensure consistent color reproduction.
• Power Savings: Manual brightness settings at high levels will increase power consumption and heat output compared to the optimized B.I.+ settings.