Why Not All 120Hz TVs Perform the Same

The Basics of Refresh Rate: What 120Hz Really Means

At its core, refresh rate is the frequency at which a TV redraws the entire image on screen. A 120Hz refresh rate means the display refreshes 120 times every second. This can be especially beneficial for fast-moving content—like sports, video games, and action films—because it reduces motion blur and enhances visual clarity.

However, it’s crucial to separate refresh rate from frame rate, which refers to how many frames per second (fps) the content is delivered in. A movie might be filmed in 24 fps, while a video game might output 60 or 120 fps. The TV’s job is to display these incoming frames at the correct pace and refresh the image as fluidly as possible.

But achieving smooth motion at 120Hz is not just about matching numbers—it’s about how the display handles the incoming signal, how quickly pixels respond to changes, and how well the TV’s internal components coordinate each cycle.

Display Panel Technology: Not All Pixels Are Equal

The first major differentiator between 120Hz TVs lies in the panel technology used. The two most common types are LCD (often with LED or Mini-LED backlighting) and OLED (Organic Light Emitting Diode). Both can be built with 120Hz capabilities, but their chemical and physical properties yield vastly different performance results. LCD panels rely on liquid crystal molecules that physically twist to modulate light. This twisting action is relatively slow and is influenced by temperature, voltage, and the specific materials used in the liquid crystal formulation. As a result, LCD panels tend to have slower response times—the time it takes for a pixel to change from one state to another.

A slower response time on a 120Hz panel can cause ghosting or motion blur, because the pixel hasn’t finished transitioning before the next refresh cycle begins. This can diminish the clarity of fast-moving images, even if the panel refreshes 120 times per second. In contrast, OLED pixels emit their own light and can switch on or off almost instantaneously. The organic compounds used in OLED displays enable far faster response times, minimizing blur and maintaining clarity at high frame rates. However, OLED performance can be impacted by peak brightness limitations and long-term material degradation—factors that don’t directly affect refresh rate but influence overall image quality.

The Role of Pixel Response Time

Having a 120Hz refresh rate means each frame is shown for about 8.3 milliseconds (1,000 ms ÷ 120 Hz). For a TV to properly display each frame without trailing effects, pixel response times need to be significantly faster—ideally below 5 ms. If a pixel takes too long to transition from one color or brightness level to another, the result is sample-and-hold blur, where remnants of the previous frame linger and interfere with the next. This can make fast-moving objects appear smeared, even though the TV is technically refreshing the image 120 times per second.

Premium 120Hz TVs use advanced panel driver circuitry and specially engineered liquid crystal compositions to speed up pixel transitions. Some employ overdrive algorithms—which apply additional voltage to accelerate pixel changes—but these must be finely tuned to avoid overshoot artifacts like inverse ghosting. Therefore, when comparing 120Hz TVs, checking the gray-to-gray response time is just as important as verifying the advertised refresh rate. A slower response time can cripple the motion performance of an otherwise high-refresh-rate panel.

Motion Interpolation and Frame Processing

Another reason 120Hz TVs differ is how they handle motion interpolation—the process of generating new frames between original ones to create smoother motion. Every brand uses proprietary algorithms for motion interpolation, with names like MotionFlow (Sony), TruMotion (LG), or Auto Motion Plus (Samsung). These algorithms analyze motion vectors between two frames, then synthesize an intermediate frame to reduce judder or improve smoothness.

High-quality interpolation engines can produce remarkably fluid motion with minimal artifacts. Low-quality engines may introduce issues like the Soap Opera Effect, edge tearing, or misaligned frames. Some TVs allow you to fine-tune the interpolation strength or turn it off entirely, while others apply it by default without user control. The quality of this motion engine depends on both processing power and software refinement, which can vary widely, even among TVs that support 120Hz.

Signal Pathway and HDMI Bandwidth

To take full advantage of 120Hz performance—especially at 4K resolution—the signal from the source device (like a game console or streaming box) must be transmitted without degradation. That requires HDMI 2.1, the latest HDMI specification offering up to 48 Gbps bandwidth, enough to support 4K at 120Hz with 10-bit color and HDR enabled. Some budget or mid-range “120Hz” TVs only have HDMI 2.0 ports, which max out at 18 Gbps. These TVs may accept a 120Hz input at 1080p or compressed 4K, but they can’t display full uncompressed 4K/120Hz content. In other cases, TVs may feature a true 120Hz panel but restrict high refresh rate access to just one HDMI port.

It’s also critical that the internal video processing pipeline can handle the bandwidth. Even with HDMI 2.1, some TVs may lack the signal decoding capabilities to properly render HDR metadata or maintain full chroma subsampling at high frame rates. So while two TVs might claim 120Hz refresh rate and HDMI 2.1, one could fully utilize those specs while the other offers only partial support, affecting sharpness, color fidelity, and input response.

Input Lag and Game Optimization

Gamers often seek out 120Hz TVs for their promise of ultra-low input lag—the delay between pressing a button and seeing the response on screen. However, input lag is not solely dependent on refresh rate. It also hinges on the TV’s internal video processing, scaling, and motion smoothing features. Many 120Hz TVs offer Game Mode settings, which bypass unnecessary processing to reduce latency. The best implementations deliver input lag as low as 5–10 milliseconds, making them suitable for fast-paced competitive gaming.

Other models—particularly those that perform extra image enhancements or frame interpolation—may have input lag exceeding 30 milliseconds, despite offering 120Hz output. This undermines the very benefit high refresh rates are supposed to provide. Some of the top-performing gaming TVs combine 120Hz refresh with Variable Refresh Rate (VRR), Auto Low Latency Mode (ALLM), and Quick Frame Transport (QFT)—all features introduced in HDMI 2.1. TVs lacking these enhancements will feel less responsive, even at identical refresh rates.

Local Dimming and Brightness Stability at High Refresh

Another often-overlooked factor is how the TV handles local dimming and brightness stability when operating at high refresh rates. Many LCD TVs use full-array local dimming (FALD) or Mini-LED backlights to improve contrast. But these systems must rapidly adjust lighting zones in sync with the refresh cycle to avoid halo effects or flickering. At 120Hz, the dimming system has half the time to respond compared to 60Hz, which can cause light leakage or lag in contrast adjustment. Premium models employ faster local dimming controllers and more precise algorithms to adapt the backlight at the same pace as frame refreshes.

OLED TVs, being self-emissive, don’t rely on backlights and therefore don’t suffer from local dimming latency. However, their Automatic Brightness Limiting (ABL) circuits may reduce peak brightness when sustained 120Hz content is detected, especially with HDR gaming. Therefore, the true visual benefit of 120Hz varies depending on how well the display’s brightness and contrast systems keep up with rapid frame cycling.

Variable Refresh Rate vs Fixed 120Hz

A fixed 120Hz refresh rate is not always the best approach for variable frame rate content, such as video games. This is where Variable Refresh Rate (VRR) technology becomes crucial. VRR enables the TV to dynamically synchronize its refresh rate with the real-time frame output of a GPU or console, eliminating screen tearing and reducing stutter.

However, not all 120Hz TVs support VRR—even if they advertise gaming features. Some models offer only partial support, working only with certain devices or limited resolutions. Others require firmware updates or have compatibility issues with FreeSync or G-Sync standards.

Without VRR, a 120Hz TV can actually introduce new motion artifacts if the frame rate fluctuates, especially between 40–90 fps. A well-implemented 120Hz VRR TV, on the other hand, offers perfectly smooth motion and consistent performance across a wide range of frame outputs.

Marketing Tricks and Fake Refresh Rates

Some TVs advertise “Motion Rate 240” or “Effective Refresh Rate 240Hz,” even though the panel only supports native 120Hz. These inflated numbers are achieved by combining frame interpolation and black frame insertion (BFI) to simulate the look of higher refresh rates.

While these technologies can enhance motion clarity, they don’t equate to true 240Hz performance. In fact, aggressive use of motion interpolation can lead to unwanted visual artifacts and the Soap Opera Effect. And black frame insertion can dim the picture or cause flicker for sensitive viewers. True 120Hz performance requires both a native 120Hz panel and the supporting hardware and software infrastructure to process, deliver, and display that content correctly.

Conclusion: Why One Spec Isn’t Enough

A 120Hz refresh rate is not a guarantee of high performance—it’s just a starting point. The actual quality of motion, clarity, and responsiveness depends on a chain of interconnected factors: pixel response time, panel chemistry, video processor strength, HDMI bandwidth, motion handling algorithms, and game optimization features.

Two TVs can both list 120Hz in their specifications, but differ drastically in how they handle real-world motion. One might deliver stunningly smooth action and low-lag gaming; the other might still stutter or blur due to weak internals or poor tuning. Understanding the science and engineering behind refresh rate performance allows you to look past the marketing and make informed decisions. It’s not just about how often your TV refreshes—it’s about how well it uses every one of those 120 cycles per second.