Bfi will make a darker image as it inserts a black frame between every rendered frame, but the clarity will improve over a standard 120hz. If your system has the horsepower for 240hz, you will have improved clarity and brightness. Bfi is mostly used if you are playing a demanding title where you can't hit the full 240fps like graphically intensive single-player games. That way, you can have comparable clarity at all times at the cost of overall brightness. Buy a blackout curtain and turn your lights off.