Causes
- Frame rate swinging near the bottom of the FreeSync range — the EX2780Q is a 27" QHD IPS panel with FreeSync Premium, and its adaptive-sync range does not extend to very low frame rates. When in-game FPS drops to the low end or dips in and out of the variable range, the backlight pulses and the panel visibly flickers. This is a well-documented behavior of FreeSync monitors when the GPU cannot hold a steady frame rate.
- Uncapped or widely fluctuating frame rates — a game or GPU running at 200+ FPS one moment and 40 FPS the next forces the monitor's refresh rate to chase wildly, producing brightness flicker and micro-stuttering. Uncapped menus, cutscenes, and loading screens are the worst offenders because they swing outside the range entirely.
- HDRi, Vivid, or Brightness Intelligence modes fighting the adaptive-sync engine — the EX2780Q's HDRi and automatic brightness features continuously adjust backlight levels, which can visually clash with FreeSync's own brightness adjustments and cause a pulsing/flickering image in bright or dark scenes.
- FreeSync delivering a flaky signal over HDMI — on this model FreeSync Premium works over both DisplayPort and HDMI, but the HDMI 2.0 adaptive-sync handshake is less reliable on some GPU/driver combinations. A loose handshake causes intermittent flicker that disappears over DisplayPort.
- Outdated or conflicting GPU driver — an old or beta graphics driver with a poor Freesync (Adaptive-Sync) implementation can cause the EX2780Q to flicker during games even when the rest of the system is fine.
How to Fix
- Disable FreeSync to confirm the cause — press the joystick on the back of the monitor (or use the remote), open the Gaming menu, and set AMD FreeSync Premium to Off. If the flicker stops, adaptive-sync is the trigger and you can then tune the settings below rather than leave the monitor faulty.
- Use a DisplayPort connection for the most reliable FreeSync — the EX2780Q carries its full 2560x1440 @ 144Hz and cleanest FreeSync handshake over its DisplayPort 1.4 input. If you are on HDMI, switch to the included (or a VESA-certified) DisplayPort cable and confirm in the OSD Input menu that you are on the DP input.
- Cap your frame rate inside the 48-144Hz range — enable a frame limit that keeps FPS steady under 144Hz and above the FreeSync floor (for example 120 or 138Hz). Use the game's built-in limiter, AMD Freesync/Chill, or an in-engine cap. A stable, capped frame rate is the single most reliable way to stop range-swing flicker.
- Tone down HDRi, Vivid, and auto-brightness modes — in the OSD's Picture and Color menus, switch HDRi / Brightness Intelligence to Off and set the picture mode to Standard or Game (not Vivid) while FreeSync is enabled. Fewer competing auto-adjustments means less backlight pulsing.
- Update the GPU driver and FreeSync settings — install the latest stable driver for your graphics card (and its companion panel software). In the AMD Adrenalin software, confirm AMD FreeSync is enabled and enhanced sync / versusync settings are not conflicting with the monitor's setting.
- Update the monitor firmware — BenQ has released firmware for the MOBIUZ series that improves adaptive-sync and HDR behavior. Check the EX2780Q support/download page for a newer firmware and apply it per the instructions with a USB stick, then re-test FreeSync.
- Factory-reset the OSD as a final step — from the OSD System menu choose the reset option to restore factory defaults, re-enable FreeSync only, and re-test. If the flicker still follows you on a second GPU/cable combination, the adaptive-sync board may be faulty and the monitor should go back under warranty.