Response Time Explained

Understanding response time requires separating marketing claims from measured reality. This guide provides the technical foundation to evaluate response time specifications critically, choose the right overdrive settings, and identify when response time actually matters for your use case versus when other specifications should take priority.

If you've shopped for a gaming monitor, you've seen "1ms response time" on virtually every product listing. Yet when we measure these monitors with high-speed cameras, most "1ms" IPS panels actually measure 3-7ms, and "1ms" VA panels often measure 8-15ms. Understanding why requires knowing what response time actually measures—and what it doesn't.

1. What Response Time Measures

Response time measures how quickly a pixel can change from one brightness level to another. The standard measurement is Gray-to-Gray (GTG): the time for a pixel to transition from one gray level to another, measured in milliseconds.

The measurement is typically taken at the fastest transition point—often from 10% gray to 90% gray, or from 90% to 10%. Manufacturers choose the transition that produces the best number. A panel might achieve 1ms for one specific transition while averaging 5ms across all transitions.

2. GTG vs. MPRT: Two Different Metrics

GTG (Gray-to-Gray)

GTG measures the physical speed of pixel transitions. It's a hardware characteristic of the panel. Lower GTG means pixels change faster, which reduces trailing/ghosting behind moving objects. GTG is measured with a photodetector or high-speed camera.

MPRT (Moving Picture Response Time)

MPRT measures perceived motion blur from the human visual system's perspective. It accounts for both pixel transition speed AND the sample-and-hold effect of modern displays. Even a display with 0ms GTG would show motion blur due to sample-and-hold if it doesn't use backlight strobing.

MPRT is typically much higher than GTG. A 144Hz display with 1ms GTG might have 6.9ms MPRT (one frame period). Backlight strobing (ULMB, DyAc) reduces MPRT by turning the backlight off between frames, but introduces brightness reduction.

3. How Overdrive Works

Liquid crystal molecules have a natural response speed limited by their viscosity. To speed up transitions, monitors apply overdrive voltage—a higher-than-normal voltage that forces the crystals to move faster.

The challenge: if overdrive voltage is too high, the crystals overshoot their target position and must correct back. This creates inverse ghosting (also called "coronas")—bright halos around moving dark objects. Finding the right overdrive level balances speed against overshoot artifacts.

Most monitors offer multiple overdrive settings (Normal, Fast, Faster, Fastest). Our testing consistently shows that "Fastest" settings introduce visible inverse ghosting that is more distracting than the speed benefit. "Fast" or "Normal" typically provides the best balance.

4. Why "1ms" Claims Are Misleading

Manufacturers measure and report the single fastest transition on their panel, often with maximum overdrive enabled. This creates several problems:

• Cherry-picked transitions: The reported 1ms might be for one specific gray-to-gray transition. Average GTG across all transitions is typically 3-5x higher.
• Maximum overdrive: The 1ms measurement often uses overdrive settings that introduce severe inverse ghosting in real use.
• VA panel deception: VA panels have particularly slow dark-to-dark transitions (black smearing). A VA panel might achieve 1ms for bright transitions while measuring 15ms+ for dark transitions—the exact scenario that causes visible ghosting in dark game environments.

5. Real-World Response Time by Panel Type

Based on our high-speed camera measurements at optimal overdrive settings:

• OLED: 0.01-0.1ms GTG — genuinely fast, no overdrive needed
• Fast IPS (LG Nano IPS, AU Optronics AHVA): 2-5ms average GTG
• Standard IPS: 4-8ms average GTG
• TN: 1-4ms average GTG
• VA (bright transitions): 3-8ms GTG
• VA (dark transitions): 8-20ms GTG — the black smearing problem

6. What Response Time Actually Matters For

For most users, response time differences below 5ms are imperceptible in normal use. The scenarios where response time matters:

• Competitive FPS gaming: Fast response time reduces trailing behind moving targets. At 240Hz, each frame is 4.17ms—response times above this create visible ghosting.
• Dark game environments: VA black smearing is most visible in dark games with fast camera movement. IPS or OLED is strongly preferred for these games.
• High refresh rate gaming: At 144Hz+, faster response times provide more benefit because frame times are shorter.

For office work, photo editing, and casual gaming, response time is rarely a meaningful factor. Focus on panel type, color accuracy, and resolution instead.