What Is Ultra-Low Motion Blur (ULMB)?

Ultra-Low Motion Blur (ULMB) is NVIDIA's brand name for a backlight strobing mode built into G-SYNC LCD monitors. Instead of leaving the LED backlight on continuously, the monitor flashes it briefly once per refresh cycle, so your eyes only see each frame for a fraction of a millisecond rather than the full frame duration. The result is dramatically sharper moving images, similar to what a CRT delivered.

From a display engineering standpoint, ULMB is not a response-time trick. It attacks a different problem entirely: persistence blur.

Why LCDs blur motion in the first place

Every modern flat panel is a sample-and-hold display. A frame is drawn, then held static on screen until the next one arrives. When you track a moving object with your eyes, your gaze slides continuously while the image sits still for the whole frame, and the object smears across your retina.

The rule of thumb I use on the bench is Blur Busters Law: one millisecond of persistence produces one pixel of blur at 1,000 pixels per second of motion. On a 240 Hz panel that means roughly 4 pixels of blur no matter how fast the liquid crystal switches. This is why an OLED with sub-millisecond GtG still blurs at 60 Hz; the pixel transition is fast but the frame is visible for the full 16.7 ms.

Strobing sidesteps this. When the backlight is only lit for, say, 1 ms per frame, the visible persistence drops to 1 ms regardless of the refresh rate.

How the original ULMB worked (2015)

The first-generation implementation was straightforward but came with real compromises. According to NVIDIA, ULMB disabled the backlight 75% of the time, and that 25% duty cycle on a panel rated for roughly 300 nits meant images were clear but noticeably dimmer. Because 2015-era pixel response was slow, the monitor had to wait longer for pixels to settle before flashing, so ULMB reduced the refresh rate to give the crystals more time to transition. In practice that meant capping a 144 Hz or 240 Hz monitor at 120 Hz or lower.

The other limitation is architectural: ULMB and variable refresh rate could not run together. Strobing needs a fixed, predictable frame cadence to time the backlight pulse, while G-SYNC VRR deliberately varies it. Gamers had to pick one.

Most competitive players I worked with chose full refresh rate and full brightness over the blur reduction, which is why ULMB stayed a niche feature.

ULMB 2 (2023): full refresh rate, double brightness

NVIDIA reworked the technology in 2023. ULMB 2 delivers full refresh rate backlight strobing, nearly 2x higher brightness, and practically zero crosstalk compared to the original. The key engineering change is a technique NVIDIA calls Vertical Dependent Overdrive. Because a backlight lights the whole panel at once while the pixels update in a top-to-bottom rolling scanout, a portion of the screen will always show double images unless something compensates for it. With the G-SYNC module controlling the response time depending on where the vertical scan is, the pixels throughout the panel reach the right level at precisely the right time for the backlight to be flashed. This is what suppresses strobe crosstalk, the faint ghost image that plagued earlier strobing implementations.

NVIDIA quantifies the result with a metric it calls effective motion clarity. The formula is Refresh rate × (1 / Duty Cycle), so a 360 Hz monitor with ULMB 2 achieves an effective motion clarity of 1,440 Hz. Blur Busters, whose pursuit camera method is used by most professional monitor review labs, confirmed the claim is correct specifically for display persistence during eye tracking. That qualifier matters: strobing reduces tracking blur, but it does not add frames, so stroboscopic stepping during fixed-gaze viewing remains.

To qualify for ULMB 2, monitors must deliver over 1,000 Hz of effective motion clarity, drive ULMB 2 at the monitor's full refresh rate, and deliver over 250 nits of brightness with minimal crosstalk. The initial hardware was narrow: the Acer Predator XB273U F and ASUS ROG Swift PG27AQN (both 27-inch 1440p 360 Hz), followed by the ASUS ROG Swift Pro PG248QP (25-inch 1080p 540 Hz) and AOC AGON AG276QSG, all AUO fast-IPS panels. Enabling it still required disabling G-SYNC VRR in the NVIDIA Control Panel, then turning on ULMB 2 in the monitor OSD.

Where ULMB stands in 2026: G-SYNC Pulsar

ULMB 2 was effectively the last fixed-refresh version of the technology. Its successor, G-SYNC Pulsar, finally solved the strobing-versus-VRR conflict. G-SYNC Pulsar displays from Acer, AOC, ASUS and MSI became available starting January 7, 2026, and Pulsar delivers variable frequency strobing, variable refresh, and variable overdrive together. Independent testing found it works with adaptive sync with no flickering as the refresh rate changes and uses a rolling scan to provide clarity from top to bottom of the screen.

Two shifts are worth noting for anyone specifying displays. First, the hardware model changed: the original G-SYNC required a dedicated module, whereas for Pulsar NVIDIA collaborated with MediaTek to build G-SYNC directly into the display scaler, which should broaden adoption. Second, NVIDIA has been iterating via firmware; firmware 1.1.4 eliminated sharp double images below 90 FPS and added a fixed 60 Hz strobing mode for games locked to 60 Hz.

From my perspective, the competitive landscape has also moved. High-refresh OLEDs now reach 480 Hz to 720 Hz natively, and 1,000 Hz-class LCD panels have been announced. As TFTCentral put it, Pulsar does not render OLED monitors obsolete; there is far more to a display than motion clarity alone. Strobed LCDs still win on raw persistence per hertz, while OLED wins on contrast, viewing angle and freedom from flicker.

Practical trade-offs to know before you buy or specify

• Flicker sensitivity. Strobing is flicker by definition. At 120 Hz most people do not perceive it consciously, but some users report eye fatigue during long sessions. Rolling-scan implementations like Pulsar are gentler than the global flash of the original ULMB.
• Frame rate must match. Strobing only looks clean when the game holds a frame rate at or near the strobe rate. Drop to half the refresh rate and you get double images, exactly as 30 fps on a 60 Hz CRT did. Pulsar's variable-frequency strobing mitigates this; ULMB 2 does not.
• Brightness ceiling. Even at double the original brightness, a strobed LCD is dimmer than the same panel unstrobed and cannot do HDR simultaneously. This is a physics constraint of the duty cycle, not a firmware limitation.
• Measurement. If you are evaluating motion performance for procurement, be aware that VESA ClearMR certification disables motion blur reduction technologies such as backlight strobing during testing. A ClearMR tier tells you nothing about how a monitor performs with ULMB or Pulsar engaged; you need pursuit-camera photographs or an MPRT measurement in strobe mode for that.

Bottom line

ULMB is backlight strobing done with tight synchronisation between the panel's scanout, its overdrive and the backlight pulse. The 2015 original proved the concept but forced users to give up brightness, refresh rate and VRR. ULMB 2 removed the first two penalties in 2023. G-SYNC Pulsar removed the third in 2026. If your priority is target tracking in fast shooters on an LCD, a Pulsar or ULMB 2 monitor remains the clearest motion you can buy; if you value HDR, contrast and zero flicker, a high-refresh OLED is the better all-round choice.