UFO Test — Monitor Ghosting, Motion Blur & Overdrive Test

Understanding Motion Blur and Display Ghosting

When playing fast-paced games, scrolling text documents, or editing 60 FPS video, the human eye constantly engages in smooth pursuit tracking—smoothly sweeping across your visual field to follow moving objects. However, almost all modern flat-panel displays (LCDs, OLEDs, and Mini-LEDs) utilize a sample-and-hold architecture.

In a sample-and-hold display, each rendered frame remains statically illuminated on the screen for the entire duration of the refresh cycle (e.g. 16.67 ms at 60 Hz, or 6.94 ms at 144 Hz) until the next frame instantaneously replaces it. Because your eye moves continuously while the display holds each image still, the image is smeared across your retina.

+-------------------------------------------------------------+
|               The Two Components of Motion Blur             |
|                                                             |
|  Total Perceived Blur = Pixel Transition Time (GtG)         |
|                       + Eye Tracking Persistence (MPRT)     |
|                                                             |
|  [Slow LCD]   ===> 15ms GtG + 16.7ms MPRT = 31.7ms Blur     |
|  [Fast IPS]   ===> 3.5ms GtG + 6.9ms MPRT = 10.4ms Blur     |
|  [Fast OLED]  ===> 0.03ms GtG + 4.1ms MPRT = 4.13ms Blur    |
+-------------------------------------------------------------+

Display ghosting specifically refers to the optical blur contributed by sluggish pixel response times (GtG). When the liquid crystals in your panel cannot twist fast enough to match the refresh cycle, remnants of past frames trail behind high-contrast moving edges.

The Physics of LCD Overdrive and Inverse Ghosting

To accelerate sluggish liquid crystal transition times, monitor engineers developed Response Time Compensation (RTC), commonly referred to as Overdrive.

Under standard static voltage, changing an LCD crystal from dark grey to light grey might take 12 to 16 milliseconds. With Overdrive enabled, the monitor controller applies an intentional temporary voltage spike—overshooting the target steady-state voltage—to rapidly force the liquid crystals into position, before cutting voltage back to the target operating level.

   Voltage
      ^
      |         /---\  <-- Overdrive Voltage Spike (Accelerates crystals)
      |        /     \
Target+-------/       \------------------ Normal Steady Voltage
      |      /
      |     /
    0 +----+----------------------------> Time (ms)

However, if the monitor manufacturer tunes this overdrive voltage too aggressively:

1. Normal Ghosting (Underdrive): Overdrive is OFF or set too low. Pixels take too long to transition, creating a soft, dark, blurry tail behind moving elements.
2. Optimal Overdrive: Pixels transition crisply within the frame window with minimal trailing and zero discoloration.
3. Inverse Ghosting / Corona (Overdrive Overshoot): Overdrive is pushed to maximum. The liquid crystals overshoot past their target color, creating jarring glowing white, blue, or inverted silhouette halos around moving objects.

GtG (Grey-to-Grey) vs MPRT (Moving Picture Response Time)

Many monitor marketing sheets advertise “1ms Response Time”, but fail to clarify whether they are quoting Grey-to-Grey (GtG) or Moving Picture Response Time (MPRT):

1. Grey-to-Grey (GtG)

GtG represents the raw physical transition time required for a subpixel to shift from one shade of grey to another (typically measured between 10% and 90% luminance).

• On a 60 Hz monitor, the refresh cycle lasts 16.67 ms. If GtG is 12 ms, pixels finish transitioning just before the next frame arrives.
• On a 240 Hz monitor, each frame window is only 4.17 ms. If GtG is slower than 4.17 ms, pixel transitions bleed into adjacent frames, producing persistent ghost trails.

2. Moving Picture Response Time (MPRT)

MPRT measures how long an image pixel remains continuously illuminated and visible on your retina. Even on a hypothetical display with instantaneous 0.00ms GtG (such as an OLED), motion blur still occurs because your eyes track continuously while the frame remains static on screen. MPRT is mathematically bounded by refresh rate:

MPRT_{Sample-and-Hold} \approx \frac{1000}{Refresh Rate (Hz)}  ms

At 60 Hz, baseline MPRT is 16.67 ms. At 144 Hz, baseline MPRT is 6.94 ms. At 360 Hz, baseline MPRT drops to 2.78 ms. This explains why high refresh rates inherently improve motion clarity even on identical LCD panels.

Panel Technology Comparison: IPS vs VA vs TN vs OLED

Different display panel architectures have fundamentally different liquid crystal physics:

If you notice that text smudges noticeably into a black smudge when scrolling web pages in Dark Mode on your monitor, your display is almost certainly a VA (Vertical Alignment) panel struggling with dark-level transitions.

Brand-by-Brand OSD Overdrive Calibration Guide

Every major display manufacturer uses different terminology for Overdrive in their On-Screen Display (OSD) menus. Use this calibrated cheat sheet to eliminate ghosting without triggering inverse halos:

1. ASUS Monitors (ROG & TUF Gaming)

• Menu Setting: Image › Trace Free.
• Scale: 0 to 100 (in increments of 20: 0, 20, 40, 60, 80, 100).
• Recommended Setting: Trace Free 60.
• Why: Trace Free 80 and 100 introduce extreme white coronas around moving characters, while 0 and 20 cause heavy trailing blur.

2. LG UltraGear Monitors

• Menu Setting: Game Adjust › Response Time.
• Options: Off, Normal, Fast, Faster.
• Recommended Setting: Fast.
• Why: The Faster preset is tuned solely to hit advertised 1ms marketing claims in laboratories, producing catastrophic inverse ghosting during real-world gameplay.

3. Samsung Odyssey Monitors (G5, G7, G9)

• Menu Setting: Game › Response Time.
• Options: Standard, Faster, Extreme, Extreme (MBR).
• Recommended Setting: Faster (or Extreme (MBR) if backlight strobing is desired).
• Why: Extreme causes noticeable ringing artifacts on fast camera pans.

4. BenQ ZOWIE Esports Monitors

• Menu Setting: Picture › AMA (Advanced Motion Accelerator).
• Options: Off, High, Premium.
• Recommended Setting: High.
• Why: Premium causes intense purple/cyan corona overshoot behind player crosshairs.

5. Dell & Alienware Gaming Displays

• Menu Setting: Game › Response Time.
• Options: Fast, Super Fast, Extreme.
• Recommended Setting: Fast or Super Fast (depending on native refresh rate).
• Why: Extreme mode produces visible dark-to-light edge doubling.

Environmental Temperature and “Winter Ghosting”

A rarely discussed physical phenomenon in display engineering is the effect of ambient room temperature on liquid crystal response time.

Nematic liquid crystals are organic fluid compounds. In cold environments—such as an unheated office during winter (temperatures below 15°C / 59°F)—the dynamic viscosity of the liquid crystal fluid increases significantly. This mechanical resistance slows down molecular rotation, causing temporary but severe motion trailing and smearing on displays that usually look crisp.

Once the monitor has been powered on for 20 to 30 minutes, the internal heat generated by the LED backlight array elevates the internal panel cavity temperature to its standard 35°C – 45°C operating range, returning liquid crystal viscosity to normal.

How to Conduct an Accurate Pursuit Camera Test

While visual observation using this online UFO Test provides immediate feedback, capturing definitive photographic evidence for RMA warranty claims or hardware reviews requires mimicking a pursuit camera:

1. Mount Your Smartphone on a Stable Track or Smooth Slider: Ensure your camera lens is completely parallel to the display panel surface.
2. Set Camera Shutter Speed: Configure manual camera controls in Pro mode to four times your monitor’s refresh interval (e.g., 1/60s for 240Hz, or 1/30s for 120Hz).
3. Match Horizontal Tracking Velocity: Slide the smartphone along a flat ruler or desk rail from left to right at the exact speed of the 960 px/sec UFO.
4. Inspect the Vertical Sync Bars: When your camera tracking speed matches the UFO speed, the vertical white calibration lines will photograph as razor-sharp single lines rather than doubled or quadrupled ghost images.

Motion Blur Reduction (Backlight Strobing): DyAc, ULMB, and ELMB

If you demand the absolute pinnacle of motion clarity for competitive first-person shooters (CS2, Valorant, Overwatch 2), consider enabling your monitor’s backlight strobing technology:

• NVIDIA ULMB / ULMB 2: Ultra Low Motion Blur.
• BenQ DyAc / DyAc+ / DyAc 2: Dynamic Accuracy.
• ASUS ELMB / ELMB-Sync: Extreme Low Motion Blur.

How Backlight Strobing Works

Instead of leaving the LED backlight continuously on (sample-and-hold), strobing technology pulses the backlight completely dark during the period when liquid crystals are transitioning between states, illuminating the panel only when pixels have fully settled. This effectively drops MPRT down to 0.5 ms – 1.0 ms, providing CRT-like motion clarity where text remains legible even during rapid 1440 px/s pans.

[!NOTE] Backlight strobing reduces overall panel peak brightness (typically from 400 nits down to 220–280 nits) and may introduce subtle flicker for individuals sensitive to pulse-width modulation (PWM).

After tuning your monitor overdrive, verify your frame stability with our companion Refresh Rate Test, inspect your screen for dropped frames using the Frame Skipping Test, and check overall color uniformity with the Screen Uniformity Test.