Causes
- VRR (G-Sync Compatible / FreeSync Premium) luminance fluctuation — the 27GP850-B is a Nano IPS panel whose backlight visibly jumps in brightness while variable refresh is active and the frame rate dips toward or below the VRR floor (roughly below 45–50 fps), which happens constantly in loading screens, menus, and open-world traversal. Owners report the whole screen flickers or pulses, and that toggling G-Sync/FreeSync off and back on is the quickest confirmation.
- HDR switched on for SDR content — with HDR enabled, the panel's tone mapping makes the backlight oscillate between two very similar brightness levels (occasionally with a 1-frame horizontal black bar near the top), a pattern owners see on the desktop, in Adobe Premiere, and in games. Because this model has no local dimming, HDR relies entirely on backlight control, which shows this instability.
- OSD Power Saving / Eco Mode left enabled — the 27GP850-B's Power Saving, Eco Mode, and Energy Saver settings cycle the backlight even when a static image is shown, and users report random flicker that only stops once these are turned off. This is often the culprit behind intermittent flicker that happens at idle rather than during gameplay.
- Loose, bent, or low-bandwidth DisplayPort link — to carry 2560x1440 at 165Hz the 27GP850-B needs a solid DisplayPort 1.4 connection. A partially seated DP connector, an old or defective cable, or daisy-chaining through an adapter lets the link drop or resync, producing brief single black frames or bright flicker, and multi-monitor setups can glitch the input as a second display renders.
- Outdated or unstable GPU driver — a Windows or GPU driver update that conflicts with VRR/refresh handling can cause sustained flicker on this panel, and the issue usually clears with a clean driver install.
How to Fix
- Turn off Power Saving / Eco Mode in the OSD — press the joystick button to open the menu, go to General → Energy Saving and set it to Off, and disable Power Saving and Eco Mode wherever they appear. This removes the standby backlight cycling that causes idle flicker.
- Sort out variable refresh (G-Sync / FreeSync) — in the OSD open the Game Adjust menu and toggle Adaptive-Sync / FreeSync Off, then On again to reset the handshake. If the flicker appeared mainly while VRR was active, cap the in-game frame rate to a stable value above the VRR floor (for example using a limit of ~140 fps at 144Hz) so it no longer swings below the range. On NVIDIA, confirm G-Sync is set for fullscreen in the Control Panel if you want to keep it.
- Disable HDR for SDR use — open Windows Settings → System → Display, select the 27GP850-B, and turn HDR Off when running desktop/office/photo work. Enable HDR only for HDR games or video. If the brightness oscillation was HDR-related, this stops it immediately.
- Reseat and swap the DisplayPort cable — power everything down, unplug the DP connector from both ends, check for bent pins, and re-seat it so the DisplayPort latch clicks fully. Use a certified DisplayPort 1.4 cable plugged directly into the GPU (not through an adapter or a front-panel port), and try the second DP input on the monitor to rule out a bad port.
- Update or cleanly reinstall the GPU driver — install the latest stable driver for your GPU; if flicker persists, use Display Driver Uninstaller (DDU) in Safe Mode and reinstall fresh, since a conflicting driver update is a known trigger on this panel.
- Power-cycle and isolate multi-monitor — unplug the 27GP850-B for 30 seconds, reconnect, and briefly use it as the only display to confirm a second monitor isn't glitching the input. Confirm the monitor input is set to the cable you are using.
- If it still flickers on another device, use the warranty — connect a different PC or laptop on a known-good cable. If the panel keeps flickering regardless, the backlight or scaler board is faulty and should be serviced under LG's warranty.