BFI for Gaming Black Frame Insertion (motion blur reduction for games)

What BFI for gaming is

Black frame insertion, called BFI, motion blur reduction, or strobing depending on the maker, switches the image off for part of each refresh cycle. The purpose is to fix a problem that fast pixels do not fix. As black frame insertion explains for video, LCD and OLED screens are sample-and-hold displays: they draw a frame and keep showing it until the next one arrives. TFTCentral states the effect applies "even if response times were instantaneous (0ms) and even at 120Hz/144Hz high refresh rate," because your eye keeps tracking across a frame that does not move.

How BFI works

The hold time per frame is the reciprocal of the refresh rate: 16.7 ms at 60 Hz, 8.3 ms at 120 Hz, 6.9 ms at 144 Hz, 4.2 ms at 240 Hz, and 2.1 ms at 480 Hz. KTC's worked estimate for an object crossing the screen at 960 pixels per second smears across about 16 pixels at 60 Hz, 8 pixels at 120 Hz, and 4 pixels at 240 Hz. Higher refresh rates shorten the hold but never reach zero. A CRT phosphor, by comparison, decays in roughly 1 to 2 ms.

BFI shortens the visible time instead. Persistence equals the frame time multiplied by the share of the cycle the image is lit (the duty cycle). Wikipedia reports that LG's 2020 and 2021 WOLED TVs run BFI at 120 Hz with a duty cycle as low as 38%, which gives 8.33 ms x 0.38 = 3.2 ms, the "mere 3.2 ms of persistence" figure it cites, comparable to a plain sample-and-hold OLED at roughly 310 Hz. At 960 pixels per second, 3.2 ms of persistence leaves about 3 pixels of smear. Backlight-strobing LCD monitors use the same idea with a flashing backlight. TFTCentral measured the LightBoost mode on the Asus VG278HE at 120 Hz with the backlight lit for about 2.4 ms per refresh, and it measured Asus ULMB on the PG278Q at a 1.875 ms pulse at its 100 setting.

BFI vs higher refresh rate

Both attack persistence, but they cost different things. Going from 120 Hz to 240 Hz halves the hold time from 8.3 ms to 4.2 ms and needs a faster panel, more GPU output, and a cable that carries it. BFI at 120 Hz with a 38% duty cycle reaches 3.2 ms from the same signal, so on a TV limited to 4K at 120 Hz it is the cheaper route to a sub-4 ms image. TFTCentral found LightBoost cut motion blur by 85% to 92% against 60 Hz, with a best case of 1.4 ms against 16.7 ms. The catch is that the light is gone for most of each cycle, so the other metrics suffer.

What BFI costs

Brightness. Less lit time means less light. TFTCentral recorded a drop from 120 cd/m2 to 88 cd/m2 on LightBoost, from about 282 cd/m2 to 118.6 cd/m2 on BenQ Blur Reduction, from about 385 cd/m2 to 123 cd/m2 on ULMB, and from nearer 400 cd/m2 to 257 cd/m2 on Eizo Turbo 240. That is a loss of 27% to 68% across four implementations, so BFI is a poor partner for HDR highlights.

Flicker. The site notes flicker is more apparent at lower strobe rates, and an 85 Hz strobe looks more flickery than a 144 Hz one. A 60 Hz BFI mode on a TV flickers at 60 Hz, which some viewers notice and some do not.

Variable refresh rate. Strobing needs a fixed frequency so the pulse timing stays constant, and VRR varies the refresh rate frame by frame. TFTCentral states ULMB "cannot be used at the same time as G-sync," and KTC notes that enabling NVIDIA ULMB 2 disables G-SYNC. Plan on choosing motion clarity or VRR, and see VRR flicker for the related brightness fluctuation on OLED. Frame pacing matters too: a BFI mode only looks clean when the game holds a locked frame rate that matches the refresh rate.

Crosstalk. TFTCentral defines strobe crosstalk as "a ghosting trail image on the screen behind moving objects," and says it falls as refresh rate rises.

Which displays offer it

LG's 2021 page says OLED Motion Pro "inserts black data of adaptive duration to reduce motion blur" and lists it on the G1, C1, and B1. I could not fetch a page that confirms which later LG models dropped the 120 Hz BFI option, so check the exact model's motion settings before buying for this feature. On monitors, the vendor names are LightBoost, ULMB, and Blur Reduction, and Eizo's Turbo 240 flashes the backlight twice per frame. VESA's ClearMR program, announced on 22 August 2022 with tiers from ClearMR 3000 to ClearMR 9000, turns backlight strobing off during testing, so a ClearMR tier describes the panel and not its strobed mode. For TV picks see the best TV for gaming guide, and read motion resolution and MPRT for how persistence is measured.

When to use it

BFI pays off with locked frame rates and fast lateral motion: racing games, side-scrollers, and competitive shooters at a steady 120 fps. It does little for slow camera pans, static scenes, or games that swing between 45 and 90 fps. KTC's rule of thumb is to use it when motion clarity matters more than maximum brightness, flicker tolerance, or VRR flexibility. Pair it with Game Mode for the rest of the low-latency settings.