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The refresh rate, also known as vertical refresh rate, vertical scan rate or vertical frequency in reference to terminology originating with cathode-ray tubes (CRTs), is the number of times per second that a raster-based display device displays a new image. This is independent from frame rate, which describes how many images are stored or generated every second by the device driving the display. On CRT displays, higher refresh rates produce less flickering, thereby reducing eye strain. In other technologies such as liquid-crystal displays, the refresh rate affects only how often the image can potentially be updated.[1]

Non-raster displays may not have a characteristic refresh rate. Vector displays, for instance, do not trace the entire screen, only the actual lines comprising the displayed image, so refresh speed may differ by the size and complexity of the image data.[2] For computer programs or telemetry, the term is sometimes applied to how frequently a datum is updated with a new external value from another source (for example; a shared public spreadsheet or hardware feed).

Physical factors

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While all raster display devices have a characteristic refresh rate, the physical implementation differs between technologies.

Cathode-ray tubes

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Electron beam in the process of refreshing an image on a CRT

Raster-scan CRTs by their nature must refresh the screen since their phosphors will fade and the image will disappear quickly unless refreshed regularly.

In a CRT, the vertical scan rate is the number of times per second that the electron beam returns to the upper left corner of the screen to begin drawing a new frame.[3] It is controlled by the vertical blanking signal generated by the video controller, and is partially limited by the monitor's maximum horizontal scan rate.

The refresh rate can be calculated from the horizontal scan rate by dividing the scanning frequency by the number of horizontal lines, plus some amount of time to allow for the beam to return to the top. By convention, this is a 1.05x multiplier.[4] For instance, a monitor with a horizontal scanning frequency of 96 kHz at a resolution of 1280 × 1024 results in a refresh rate of 96,000 ÷ (1024 × 1.05) ≈ 89 Hz (rounded down).

CRT refresh rates have historically been an important factor in video game programming. In early videogame systems, the only time available for computation was during the vertical blanking interval, during which the beam is returning to the top right corner of the screen and no image is being drawn.[5] Even in modern games, however, it is important to avoid altering the computer's video buffer except during the vertical retrace, to prevent flickering graphics or screen tearing.

Liquid-crystal displays

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Unlike CRTs, where the image will fade unless refreshed, the pixels of liquid-crystal displays retain their state for as long as power is provided. Consequently, there is no intrinsic flicker regardless of refresh rate. However, the refresh rate still determines the highest frame rate that can be displayed, and despite there being no actual blanking of the screen, the vertical blanking interval is still a period in each refresh cycle when the screen is not being updated, during which the image data in the host system's frame buffer can be updated. Vsync options can eliminate screen tearing by rendering the whole image at the same time.

Computer displays

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A video of a CPU fan rotating at 0, 300 and 1300 revolutions per minute, recorded at 60 frames per second

On smaller CRT monitors (up to about 15 in or 38 cm), few people notice any discomfort between 60–72 Hz. On larger CRT monitors (17 in or 43 cm or larger), most people experience mild discomfort unless the refresh is set to 72 Hz or higher. A rate of 100 Hz is comfortable at almost any size. However, this does not apply to LCD monitors. The closest equivalent to a refresh rate on an LCD monitor is its frame rate, which is often locked at 60 fps. But this is rarely a problem, because the only part of an LCD monitor that could produce CRT-like flicker—its backlight—typically operates at around a minimum of 200 Hz.

Different operating systems set the default refresh rate differently. Microsoft Windows 95 and Windows 98 (First and Second Editions) set the refresh rate to the highest rate that they believe the display supports. Windows NT-based operating systems, such as Windows 2000 and its descendants Windows XP, Windows Vista and Windows 7, set the default refresh rate to a conservative rate, usually 60 Hz. Some fullscreen applications, including many games, now allow the user to reconfigure the refresh rate before entering fullscreen mode, but most default to a conservative resolution and refresh rate and let you increase the settings in the options.[citation needed]

Old monitors could be damaged if a user set the video card to a refresh rate higher than the highest rate supported by the monitor. Some models of monitors display a notice that the video signal uses an unsupported refresh rate.

Dynamic refresh rate

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See also: Variable refresh rate

Some LCDs support adapting their refresh rate to the current frame rate delivered by the graphics card. Two technologies that allow this are FreeSync and G-Sync.

Stereo displays

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When LCD shutter glasses are used for stereo 3D displays, the effective refresh rate is halved, because each eye needs a separate picture. For this reason, it is usually recommended to use a display capable of at least 120 Hz, because divided in half this rate is again 60 Hz. Higher refresh rates result in greater image stability, for example 72 Hz non-stereo is 144 Hz stereo, and 90 Hz non-stereo is 180 Hz stereo. Most low-end computer graphics cards and monitors cannot handle these high refresh rates, especially at higher resolutions.

For LCD monitors the pixel brightness changes are much slower than CRT or plasma phosphors. Typically LCD pixel brightness changes are faster when voltage is applied than when voltage is removed, resulting in an asymmetric pixel response time. With 3D shutter glasses this can result in a blurry smearing of the display and poor depth perception, due to the previous image frame not fading to black fast enough as the next frame is drawn.[citation needed]

Televisions

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This gif animation shows a rudimentary comparison of how motion varies with 4 Hz, 12 Hz, and 24 Hz refresh rates. Entire sequence has a frame rate of 24 Hz.[6]

The development of televisions in the 1930s was determined by a number of technical limitations. The AC power line frequency was used for the vertical refresh rate for two reasons. The first reason was that the television's vacuum tube was susceptible to interference from the unit's power supply, including residual ripple. This could cause drifting horizontal bars (hum bars). Using the same frequency reduced this, and made interference static on the screen and therefore less obtrusive. The second reason was that television studios would use AC lamps, filming at a different frequency would cause strobing.[7][8][9] Thus producers had little choice but to run sets at 60 Hz in America, and 50 Hz in Europe. These rates formed the basis for the sets used today: 60 Hz System M (almost always used with NTSC color coding) and 50 Hz System B/G (almost always used with PAL or SECAM color coding). This accident of chance gave European sets higher resolution, in exchange for lower frame rates. Compare System M (704 × 480 at 30i) and System B/G (704 × 576 at 25i). However, the lower refresh rate of 50 Hz introduces more flicker, so sets that use digital technology to double the refresh rate to 100 Hz are now very popular. (see Broadcast television systems)

Another difference between 50 Hz and 60 Hz standards is the way motion pictures (film sources as opposed to video camera sources) are transferred or presented. 35 mm film is typically shot at 24 frames per second (fps). For PAL 50 Hz this allows film sources to be easily transferred by accelerating the film by 4%. The resulting picture is therefore smooth, however, there is a small shift in the pitch of the audio. NTSC sets display both 24 fps and 25 fps material without any speed shifting by using a technique called 3:2 pulldown, but at the expense of introducing unsmooth playback in the form of telecine judder.

Similar to some computer monitors and some DVDs, analog television systems use interlace, which decreases the apparent flicker by painting first the odd lines and then the even lines (these are known as fields). This doubles the refresh rate, compared to a progressive scan image at the same frame rate. This works perfectly for video cameras, where each field results from a separate exposure – the effective frame rate doubles, there are now 50 rather than 25 exposures per second. The dynamics of a CRT are ideally suited to this approach, fast scenes will benefit from the 50 Hz refresh, the earlier field will have largely decayed away when the new field is written, and static images will benefit from improved resolution as both fields will be integrated by the eye. Modern CRT-based televisions may be made flicker-free in the form of 100 Hz technology.

Many high-end LCD televisions now have a 120 or 240 Hz (current and former NTSC countries) or 100 or 200 Hz (PAL/SECAM countries) refresh rate. The rate of 120 was chosen as the least common multiple of 24 fps (cinema) and 30 fps (NTSC TV), and allows for less distortion when movies are viewed due to the elimination of telecine (3:2 pulldown). For PAL at 25 fps, 100 or 200 Hz is used as a fractional compromise of the least common multiple of 600 (24 × 25). These higher refresh rates are most effective from a 24p-source video output (e.g. Blu-ray Disc), and/or scenes of fast motion.[10]

Displaying movie content on a TV

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As movies are usually filmed at a rate of 24 frames per second, while television sets operate at different rates, some conversion is necessary. Different techniques exist to give the viewer an optimal experience.

The combination of content production, playback device, and display device processing may also give artifacts that are unnecessary. A display device producing a fixed 60 fps rate cannot display a 24 fps movie at an even, judder-free rate. Usually a 3:2 pulldown is used, giving a slight uneven movement.

While common multisync CRT computer monitors have been capable of running at even multiples of 24 Hz since the early 1990s, recent "120 Hz" LCDs have been produced for the purpose of having smoother, more fluid motion, depending upon the source material, and any subsequent processing done to the signal. In the case of material shot on video, improvements in smoothness just from having a higher refresh rate may be barely noticeable.[11]

In the case of filmed material, as 120 is an even multiple of 24, it is possible to present a 24 fps sequence without judder on a well-designed 120 Hz display (i.e., so-called 5-5 pulldown). If the 120 Hz rate is produced by frame-doubling a 60 fps 3:2 pulldown signal, the uneven motion could still be visible (i.e., so-called 6-4 pulldown).

Additionally, material may be displayed with synthetically created smoothness with the addition of motion interpolation abilities to the display, which has an even larger effect on filmed material.

"50 Hz" TV sets (when fed with "50 Hz" content) usually get a movie that is slightly faster than normal, avoiding any problems with uneven pulldown.

See also

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References

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Revisions and contributorsEdit on WikipediaRead on Wikipedia

Refresh rate

View on Grokipedia
from Grokipedia
Refresh rate refers to the frequency at which a , such as a monitor or , updates or redraws the image on the screen, measured in hertz (Hz), where each hertz represents one complete refresh cycle per second. This specification originated with cathode-ray tube (CRT) displays, in which an electron beam scans the phosphor-coated screen from top to bottom to illuminate pixels, necessitating periodic refreshes to maintain the image and prevent flicker. In modern flat-panel technologies like liquid crystal displays (LCDs) and organic light-emitting diode (OLED) panels, the concept persists but operates differently: LCDs rely on backlights and liquid crystals to modulate light, while OLEDs emit light directly from organic compounds, yet both update pixel states at the specified rate to render dynamic content. The refresh rate plays a critical role in visual quality, particularly for motion smoothness and reducing artifacts like blur or tearing. Higher rates, such as 144 Hz, 160 Hz, 240 Hz, or 360 Hz, allow for more frequent image updates, which is especially beneficial in applications like gaming, , and fast-paced sports viewing, as they minimize the persistence of previous frames and enhance perceived fluidity. For competitive gaming, a 360 Hz refresh rate offers superior fluidity compared to 240 Hz, particularly when the system can sustain frame rates above 240 FPS. In first-person shooter (FPS) games, high refresh rates significantly reduce picture ghosting, enhance aiming smoothness, and improve reaction speed. For instance, a 60 Hz display—the standard for many consumer devices—refreshes 60 times per second, sufficient for static or slow-moving content but potentially causing noticeable judder in high-motion scenarios, whereas rates exceeding 120 Hz provide a more responsive experience when paired with compatible graphics hardware. The effective performance also depends on synchronization with the (FPS) generated by the (GPU); ideally, the frame rate matches the refresh rate exactly for optimal results. For example, on a 160 Hz Full HD (FHD) laptop screen, 160 FPS is ideal to achieve maximum smoothness, minimal motion blur, and no tearing, especially with adaptive sync technologies such as G-Sync or FreeSync, or V-Sync enabled. Higher frame rates (e.g., 200+ FPS) can reduce input lag in competitive gaming scenarios but will not be fully displayed beyond the display's 160 Hz limit, as the screen cannot present more frames than its refresh rate. Mismatches between frame rate and refresh rate can lead to issues like , often mitigated by technologies such as adaptive sync. Historically, CRT monitors supported refresh rates from 60 Hz to over 200 Hz at lower resolutions, limited by the scanning speed to avoid visible flicker, which studies have shown can impact visual performance and user comfort. In contrast, LCD and displays achieve higher rates more readily due to pixel-level control, with modern panels reaching up to 120 Hz or more and response times as low as 0.1 ms, outperforming traditional LCDs that typically operate at 60 Hz. As display technology evolves, refresh rates continue to increase, driven by demands for immersive experiences in , , and professional content creation, though they must balance with power consumption and hardware capabilities.

Fundamentals

Definition and Purpose

The refresh rate of a display refers to the number of times per second that the screen's image is redrawn or refreshed, typically measured in hertz (Hz). This process involves updating the pixels across the entire display to reflect new or ongoing visual content, ensuring that the image remains current and accurate. In essence, it quantifies how frequently the display cycles through its frame buffer to produce the visible output, distinguishing it from related concepts like , which pertains to the source content rather than the display hardware itself. The primary purpose of the refresh rate is to mitigate visual artifacts such as motion blur and , thereby delivering smoother and more immersive viewing experiences. By redrawing the image at a sufficient , displays can align with the human eye's , where afterimages linger briefly, creating the illusion of continuous motion without perceptible interruptions. Historically, this was particularly crucial in early cathode-ray tube (CRT) displays, where low refresh rates could result in visible scan lines or phosphorescent trails, compelling designers to target rates above the threshold for comfortable viewing. Today, higher refresh rates enhance clarity in dynamic scenarios, such as gaming or fast-paced video, by reducing the time between image updates and minimizing perceived judder. Human visual perception plays a key role in determining effective refresh rates, particularly through the critical —the point at which a flickering appears steady—which typically ranges from 50 to 60 Hz for most individuals under normal lighting conditions. Below this threshold, flicker becomes noticeable and can cause or fatigue, while rates above it contribute to seamless visuals by exceeding the eye's . For example, refresh rates of 144 Hz and 240 Hz provide progressively smoother motion and reduced motion blur compared to 60 Hz, with 240 Hz offering further benefits in fast-moving content like games or scrolling by lowering eye strain, although the difference between 144 Hz and 240 Hz is noticeable but smaller than that from 60 Hz to 144 Hz. There is no evidence that 240 Hz worsens fatigue due to backlight issues, and such high-refresh-rate displays often include premium features that enhance overall comfort. Factors like ambient , content contrast, and individual differences in can influence this threshold, underscoring why modern displays often exceed 60 Hz for optimal performance. The relationship between refresh rate and the time allotted for each image update is expressed by the basic equation: Refresh rate (Hz)=1Refresh interval (seconds per frame)\text{Refresh rate (Hz)} = \frac{1}{\text{Refresh interval (seconds per frame)}} This formula illustrates that a higher refresh rate corresponds to a shorter interval between redraws, directly impacting motion ; for instance, a 60 Hz rate means each frame is displayed for approximately 16.67 milliseconds.

Measurement and Units

The refresh rate of a display is quantified using the unit hertz (Hz), representing the number of complete image updates, or , per second. A 60 Hz refresh rate, for instance, indicates that the screen refreshes the entire 60 times each second, providing a baseline for smooth in standard applications. This unit applies primarily to systems, where each refresh cycle draws all lines of the frame sequentially. In historical contexts, particularly with interlaced scanning in , refresh rates were measured in fields per second rather than frames per second. Interlaced systems alternate between odd and even lines in separate fields to double the effective rate without increasing bandwidth; thus, NTSC broadcasts used approximately 59.94 fields per second (equating to 29.97 frames per second), while PAL systems employed 50 fields per second (25 frames per second). , now dominant in digital displays, directly specifies frames per second, simplifying the metric to full-frame updates. Measurement of refresh rate typically involves hardware or software techniques focused on timing signals. Using an , technicians capture and measure the period between vertical sync (V-sync) pulses, which mark the beginning of each frame; the inverse of this period yields the rate in Hz. Software-based verification employs test patterns, such as animated UFO motion tests, where users observe frame persistence or use embedded counters to confirm the rate against the display's reported capabilities. Industry standards govern acceptable refresh rates to ensure compatibility and performance. The (VESA) outlines timing formulas in its Generalized Timing Formula (GTF) standard, supporting rates like 60 Hz for common resolutions in computer monitors. The (ITU) recommends 50 Hz field rates for PAL broadcast systems in much of and , and approximately 60 Hz for in , influencing legacy and compatible displays. Common values in contemporary monitors include 60 Hz as the standard for office and media use, escalating to 144 Hz or 240 Hz in gaming models for enhanced motion clarity. This quantification helps reduce flicker by aligning updates with human visual persistence.

Physical Mechanisms

Cathode-Ray Tubes

In cathode-ray tubes (CRTs), the refresh rate is the at which an electron beam from the scans the entire phosphor-coated screen to redraw the , preventing decay into . The beam is focused and accelerated toward the screen, where horizontal deflection coils sweep it across each line from left to right at high speed, while vertical deflection coils reposition it to the next line after a brief retrace period. This raster scanning process excites phosphors to emit light proportional to beam intensity, forming visible pixels; a full top-to-bottom traversal completes one frame. CRTs support both progressive and interlaced scanning to achieve the refresh rate. Progressive scanning draws all lines sequentially within a single frame, while interlaced scanning—standard in broadcast systems like —alternates odd and even lines across two fields per frame, doubling the effective update rate for motion while halving bandwidth needs. In , this yields a 60 Hz full-frame refresh from two 30 Hz fields of 262.5 lines each, totaling . Flicker visibility arises if the beam's trace or phosphor glow fades too quickly between scans, requiring minimum refresh rates of 50-60 Hz for most viewing conditions. persistence, defined as the decay time to 10% of peak intensity, typically spans microseconds for high-speed graphics phosphors to milliseconds for types used in color CRTs (e.g., blue follows a power-law decay over ~5 ms plus exponential components). Lower-persistence phosphors demand higher rates to sustain image without flicker, as the eye integrates over ~100 ms. Before LCDs dominated in the early 2000s, high-end CRT monitors achieved refresh rates up to 120 Hz at resolutions like 1024×768, balancing phosphor excitation limits and deflection coil capabilities. The refresh rate relates to scan parameters via fv=fhNf_v = \frac{f_h}{N} where fvf_v is the vertical refresh rate, fhf_h the horizontal scan rate, and NN the number of lines per frame (progressive). For NTSC, fh=15.75f_h = 15.75 kHz and N=525N = 525 yield fv=60f_v = 60 Hz, adjusted for interlacing.

Liquid-Crystal Displays

In liquid-crystal displays (LCDs), pixels operate on a sample-and-hold principle, where each subpixel receives a voltage charge during the refresh cycle and retains that state—controlling light transmission through alignment—until the next update. Unlike impulse-based displays, this holding period introduces no inherent light persistence from the pixels themselves, but rapid across the static image during the frame interval can cause motion blur as the visual system averages the unchanged content. The continuous emission from the in traditional LCD setups amplifies these sample-and-hold artifacts, as the held states remain illuminated for the entire frame duration, prolonging the visibility of motion trails. Strobing backlights address this by pulsing the source in with the refresh—commonly at 120 Hz or 240 Hz rates—creating brief emission periods followed by , which effectively reduces and mimics impulse driving for clearer motion rendition. Liquid crystal response times, governed by the molecular twist or reorientation speed under applied fields, typically span 5–10 ms for gray-to-gray transitions in twisted nematic or in-plane switching panels, constraining the minimum viable refresh rate to avoid visible smearing. Overdrive methods counteract this by temporarily boosting voltages to hasten alignments, cutting effective transition times and enabling higher refresh rates without excessive overshoot artifacts. Contemporary LCD monitors commonly support refresh rates of 60–144 Hz for general use, with esports-oriented models achieving up to 610 Hz or higher as of late 2025 to deliver reduced input latency and enhanced fluidity in competitive scenarios. Motion blur duration in these systems is approximated by the relation Motion blur duration≈Pixel response time+1Refresh rate,\text{Motion blur duration} \approx \text{Pixel response time} + \frac{1}{\text{Refresh rate}}, where the pixel response time reflects liquid crystal settling, and the inverse refresh rate captures the sample-and-hold hold duration, together quantifying perceived blur in moving images.

Emerging Display Technologies

Organic light-emitting diode (OLED) displays utilize self-emissive organic s that generate light directly, eliminating the need for a and enabling near-instantaneous response times of under 1 ms. This rapid pixel switching supports high refresh rates without the hold-time blur seen in transmissive displays, as each pixel can turn on and off almost immediately to refresh the image. MicroLED and quantum dot-enhanced OLED (QD-OLED) technologies extend these self-emissive advantages through independent -level light emission and control, facilitating refresh rates ranging from 120 Hz to 480 Hz. Without a , these displays inherently reduce flicker compared to modulated-backlight systems, as light output is precisely managed at the level for smoother motion rendering. Despite these benefits, emerging self-emissive displays encounter challenges including risk from prolonged static content exposure and power consumption that increases with higher refresh rates due to more frequent activations. Mitigation strategies, such as shifting and periodic refreshes, help address , while efficiency improvements aim to curb power scaling. In 2025, 240 Hz televisions and monitors have achieved widespread adoption, delivering enhanced motion clarity for gaming and . The effective refresh rate in these technologies is limited by the pixel's on/off switching time, where typically achieves approximately 0.1 ms per cycle, theoretically permitting rates up to 10 kHz before other system constraints dominate. fmax⁡=1ton+toff≈10.1×10−3=10 kHzf_{\max} = \frac{1}{t_{\text{on}} + t_{\text{off}}} \approx \frac{1}{0.1 \times 10^{-3}} = 10 \, \text{kHz}

Computing Applications

Computer Monitors

In computer monitors, the standard refresh rate for office and productivity tasks is 60 Hz, which provides adequate performance for static content like document editing and web browsing without noticeable flicker for most users. This baseline ensures compatibility with common applications and hardware, meeting the needs of general desktop use where motion is minimal. For prolonged sessions involving or dynamic interfaces, rates of 75 Hz to 120 Hz are recommended to enhance smoothness and reduce perceived , as higher frequencies minimize visible refresh artifacts that can contribute to visual fatigue. guidelines suggest refresh rates above 70 Hz help avoid flicker sensitivity, which affects a subset of users and links lower rates to increased discomfort during extended viewing. Hardware constraints on refresh rates stem from interface bandwidth limitations in standards like VESA and . 1.4, with 32.4 Gbps bandwidth, supports up to 144 Hz at resolution without compression but is limited to 60 Hz at 8K (7680x4320) using (DSC). Similarly, 2.1 offers 48 Gbps, enabling 144 Hz at 4K or 60 Hz at 8K, though higher rates at ultra-high resolutions require DSC to fit within bandwidth caps. These limits arise from pixel clock rates and data throughput, where exceeding them results in reduced refresh or resolution to maintain . Users experience tangible benefits from elevated refresh rates in non-gaming contexts, such as improved fluidity in documents or browsers and more precise cursor tracking during multitasking. These enhancements stem from reduced motion blur, allowing the display to update more frequently and align better with patterns. Studies indicate that rates above 60 Hz improve , as measured by enhanced responses in tests. Higher rates are also associated with lower visual . Additionally, a high-refresh-rate screen like 240 Hz provides smooth real-time interaction for editor operations, camera movement, previewing, and debugging physical simulations in game engine environments such as Unreal Engine, enhancing efficiency in complex environment testing. As of 2025, trends in computer monitors emphasize higher refresh rates for broader applications, with ultrawide models commonly featuring 144 Hz to 240 Hz panels to accommodate expansive multitasking on 34-inch or larger screens. Laptop displays have shifted toward optimized 120 Hz TN and IPS panels, balancing portability with smoother performance for mobile professionals handling video calls or light editing. These advancements leverage LCD and emerging OLED mechanisms for faster pixel response, enabling consistent high rates without excessive power draw. For competitive gaming, refresh rates of 360 Hz offer advantages over 240 Hz when the system can sustain frame rates exceeding 240 FPS. A 360 Hz refresh rate provides superior fluidity and reduces motion blur more effectively than 240 Hz, significantly reducing picture ghosting, enhancing aiming smoothness, and improving reaction speed in fast-paced scenarios such as first-person shooters. This improvement contributes to a competitive edge in esports, where lower input lag and smoother motion perception can be critical, though the differences are subtle and subject to diminishing returns. Compared to 144 Hz, a 240 Hz refresh rate provides smoother motion and further reduces motion blur, lowering eye strain during fast-moving content like games or scrolling, particularly in prolonged sessions; the difference is noticeable but smaller than the improvement from 60 Hz to 144 Hz, with no evidence that 240 Hz worsens fatigue due to backlight strobing and often enhanced comfort from premium features such as better panel quality. Compatibility in multi-monitor setups relies on GPU capabilities to manage varying refresh rates across displays, with NVIDIA and AMD drivers allowing independent operation without forcing synchronization to the lowest common rate. Modern GPUs, such as those in the NVIDIA RTX series or AMD Radeon lineup, handle this through scalable output pipelines, ensuring each monitor runs at its native rate for optimal productivity in extended desktops. This flexibility supports configurations like a primary 120 Hz monitor paired with secondary 60 Hz displays, though mismatched rates may introduce minor desktop composition overhead resolvable via driver settings.

Frame Rates and Synchronization

In computing applications, the of rendered content, typically measured in frames per second (FPS), refers to the number of individual images generated by the (GPU) each second, such as 30 FPS or 60 FPS in many games. The display's refresh rate, in hertz (Hz), denotes how frequently the screen updates these images. For seamless visuals, the content should align with or be an integer multiple of the refresh rate to prevent issues. Ideally, the frame rate matches the refresh rate exactly—for example, 160 FPS on a 160 Hz Full HD laptop screen—to achieve optimal smoothness, minimal motion blur, and tear-free performance, particularly when using adaptive synchronization technologies such as G-Sync or FreeSync, or V-Sync. In competitive gaming scenarios, producing frame rates higher than the refresh rate (such as above 160 FPS on a 160 Hz display) can further reduce input lag by enabling faster rendering and queuing of new frames, although the display cannot show more frames than its refresh rate allows, meaning additional frames are not fully displayed. Misalignment between frame rate and refresh rate leads to visual artifacts that degrade the viewing experience. Screen tearing occurs when the GPU delivers frames asynchronously with the display's refresh cycle, causing a horizontal split where portions of two consecutive frames appear simultaneously. This artifact is most evident when the frame rate surpasses the refresh rate, for instance, 120 FPS output on a 60 Hz monitor, resulting in partial frame draws during a single refresh. Judder represents another common issue from non-integer frame-to-refresh ratios, producing uneven motion that feels stuttery. In scenarios like 24 FPS cinematic content played on a 60 Hz display, the system employs 3:2 pulldown to repeat frames—three frames shown over five refresh intervals—creating inconsistent timing since 60 is not evenly divisible by 24. This irregularity amplifies perceived motion discontinuity, particularly in fast-moving scenes. Vertical (V-Sync) addresses these synchronization problems by constraining the GPU's frame output to exact multiples of the display's refresh rate, ensuring complete are swapped only during the vertical blanking period. While effective against tearing and judder, V-Sync introduces input lag because the rendering pipeline buffers until the next refresh interval, delaying user actions from reaching the screen. At a 60 Hz refresh rate, this lag typically amounts to one full frame time of 16.7 ms. In single-frame buffering configurations with V-Sync enabled, the added input lag can be approximated as the reciprocal of the refresh rate, reflecting the wait for buffer swap: Input lag≈1Refresh rate\text{Input lag} \approx \frac{1}{\text{Refresh rate}} This highlights the direct inverse relationship, where higher refresh rates inherently reduce potential lag—for example, 8.3 ms at 120 Hz—though V-Sync still enforces constraints. As of 2025, many ray-traced games utilize upscaling technologies like DLSS to achieve frame rates of 60 FPS or higher on 144 Hz monitors, balancing visual fidelity with smooth motion and minimizing artifacts through modern GPU optimizations. For gaming setups with older graphics cards that cannot consistently produce frame rates exceeding 165-240 FPS, monitors with refresh rates in the 165-240 Hz range still provide significant benefits for smooth performance. These higher refresh rates enhance motion clarity and reduce visual artifacts such as stuttering and blur, even when the GPU output is lower than the display's capability, by allowing more frequent updates of available frames and lowering input lag compared to 60 Hz or 144 Hz displays. Technologies like variable refresh rate (VRR) further mitigate mismatches, making such monitors suitable for improved responsiveness in competitive and fast-paced games without requiring ultra-high-end hardware.

Advanced Techniques

Dynamic Refresh Rate

Dynamic refresh rate refers to the capability of a display to dynamically adjust its refresh rate in real-time based on the content being shown or the device's power requirements, allowing rates to vary between a minimum and maximum value, such as 60 Hz to 120 Hz, to optimize performance and efficiency. This approach contrasts with fixed refresh rates, where the display operates at a constant regardless of usage, and is particularly prevalent in modern mobile devices to balance visual quality with battery life. Implementation of dynamic refresh rate typically involves advanced panel controllers that monitor frame content and adjust the timing signals accordingly, enabling seamless transitions across a wide range like 1 Hz to 120 Hz in displays. In OLED screens, adaptive refresh rate dynamically adjusts the entire panel's refresh rate to balance fluency and power consumption. For static content (e.g., reading, photos, AOD), it drops to 1Hz-30Hz to save power; for dynamic content (e.g., scrolling, games, videos), it rises to 90Hz-120Hz or higher for smoothness. This is a global panel-level adjustment, distinct from pixel self-emission characteristics like local pixel on/off. These controllers use algorithms to detect static or low-motion scenes and lower the rate to conserve power, while ramping up for dynamic content like or video playback. Low-temperature polycrystalline oxide (LTPO) (TFT) technology facilitates this by combining LTPS for high-speed switching with IGZO for low-power operation, allowing finer granularity in rate adjustments. The primary benefits include significant power efficiency gains, with reductions reported up to 65% in low-refresh modes compared to fixed high rates, extending battery life in portable devices. Additionally, it enables smoother motion rendering during high-activity scenarios by increasing the rate on demand, improving user experience without constant high-power draw. However, dynamic refresh rate can introduce drawbacks such as transition artifacts, including visual stutter or judder, when switching between rates, which may briefly disrupt smoothness if not managed by sophisticated interpolation techniques. As of 2025, LTPO panels in smartphones like the iPhone 17 and Galaxy S25 series support dynamic ranges from 1-120 Hz, with ProMotion technology now available on base iPhone models, enabling ultra-low rates for always-on displays while scaling to high rates for gaming and video.

Variable Refresh Rate Systems

Variable refresh rate (VRR) systems dynamically adjust a display's refresh rate to match the (GPU) output , typically ranging from 48 Hz to 144 Hz or higher, thereby eliminating and reducing input lag associated with traditional vertical (V-Sync). This ensures that each frame is displayed as soon as it is rendered, preventing the visual artifacts that occur when fluctuate independently of the display's fixed refresh rate. By varying the refresh rate in real-time over standards like Adaptive-Sync or Variable Refresh Rate, VRR technologies provide smoother gameplay without the stuttering introduced by frame buffering in V-Sync. AMD FreeSync implements VRR as an built on VESA Adaptive-Sync, allowing compatible displays to synchronize with GPUs without requiring additional hardware. In contrast, originally relied on a dedicated hardware module embedded in the display for precise control over refresh rates, though newer G-Sync Compatible variants leverage the same Adaptive-Sync protocol for broader compatibility with GPUs. Both systems support variable ranges tailored to the display's capabilities, with overdrive mechanisms optimizing response times to minimize motion blur during rate transitions. To extend usability at lower frame rates, both FreeSync and G-Sync incorporate Low Framerate Compensation (LFC), which duplicates frames to effectively double the minimum refresh rate when the GPU output falls below half the display's minimum supported Hz. For example, on a display with a VRR range of 48-144 Hz, LFC activates if the frame rate drops below 24 FPS, allowing smooth rendering down to as low as 1 FPS on advanced models. The adaptive range itself is defined as the difference between the maximum and minimum refresh rates: Adaptive Range=max⁡(Hz)−min⁡(Hz)\text{Adaptive Range} = \max(\text{Hz}) - \min(\text{Hz}) with LFC engagement when FPS < min⁡(Hz)/2\min(\text{Hz}) / 2. By 2025, VRR has become a standard feature in virtually all gaming monitors, with FreeSync dominating due to its royalty-free implementation and widespread certification across thousands of models. Certification tiers ensure performance quality: FreeSync offers basic VRR, while Premium requires at least 120-200 Hz support with LFC, and Premium Pro adds HDR compatibility; G-Sync certifications include Compatible for standard Adaptive-Sync validation and Ultimate for hardware-module-enhanced displays with extended ranges up to 240 Hz or more.

Specialized Displays

Stereo and 3D Displays

In stereoscopic displays, the refresh rate plays a critical role in delivering separate images to each eye to simulate . Active shutter systems alternate left-eye and right-eye frames sequentially, effectively doubling the refresh rate to maintain smooth motion; for instance, a 60 frames per second (FPS) experience per eye requires a 120 Hz display refresh rate. This alternation ensures each eye receives full-resolution images without overlap, synchronized via or signals from the display. LCD shutter glasses in these systems open and close in precise alignment with the display's refresh cycles, blocking one eye while revealing the to the other. Refresh rates exceeding 100 Hz are essential to prevent —unwanted leakage between eyes—and to minimize flicker, which can cause visual ; rates below this threshold often result in noticeable ghosting or discomfort during extended viewing. Passive 3D systems, by contrast, use polarized filters on the display and glasses to direct orthogonally polarized left and right images to each eye simultaneously, allowing the full per eye but halving the vertical resolution due to interleaved lines. Higher overall refresh rates, such as 120 Hz or more, still benefit these setups by reducing temporal artifacts like , enhancing perceived smoothness without the need for mechanical shutters. These approaches present significant challenges, including a doubling of bandwidth demands to support the elevated refresh rates, which strains graphics hardware and transmission interfaces like . Additionally, insufficient refresh rates—particularly below 100 Hz—can exacerbate motion sickness symptoms, such as and disorientation, by introducing visual-vestibular mismatches during dynamic scenes. As of 2025, stereoscopic 3D displays have seen reduced adoption in general consumer markets but continue to be employed in professional cinema projectors, which typically operate at 96-144 Hz to accommodate 3D content at 48-60 FPS per eye.

Virtual and Augmented Reality

In virtual and augmented reality (VR/AR) systems, elevated refresh rates are essential to deliver fluid motion and mitigate user discomfort, particularly by synchronizing visual updates with rapid head movements. A minimum refresh rate of 90 Hz is generally required for smooth head tracking in VR headsets, as lower rates lead to noticeable judder that can induce through sensory conflicts between visual input and signals. Research indicates that rates of 120 Hz serve as a critical threshold, beyond which symptoms of and disorientation decrease substantially without proportional gains in perceived smoothness. VR/AR headsets achieve these high rates using dual independent displays—one per eye—each refreshed at the full frequency to render stereoscopic views that simulate depth, extending basic stereo principles for immersive environments. To sustain such performance amid demanding computational loads, is employed, dynamically allocating higher detail and frame rates to the foveal region of while downsampling peripherals, thereby optimizing overall system efficiency. Notable implementations include the Meta Quest series, which supports a 120 Hz mode for enhanced responsiveness in standalone VR experiences. The , an AR/VR headset, operates at 90 Hz, 96 Hz, or 100 Hz, with its 2025 M5 variant extending to 120 Hz for crisper motion in mixed-reality applications. In November 2025, announced the Steam Frame headset, a standalone VR device supporting refresh rates up to 120 Hz standard and 144 Hz experimentally, further advancing high-refresh capabilities. These rates directly impact motion-to-photon latency, approximated as: Total motion-to-photon latency (ms)≈1000Refresh rate (Hz)+Render time (ms)\text{Total motion-to-photon latency (ms)} \approx \frac{1000}{\text{Refresh rate (Hz)}} + \text{Render time (ms)} where the first term represents display persistence time, underscoring how higher refresh rates reduce inherent delays before photons reach the user's eyes. Emerging trends include refresh rates up to 144 Hz, paired with integrated eye-tracking to enable variable quality rendering—adjusting resolution and frame prioritization in real-time based on gaze direction—for even lower latency and broader accessibility in future VR/AR devices.

Television and Media

Broadcast Televisions

Broadcast television standards originated from regional analog systems designed to align with local electrical frequencies and early technological constraints. In the , the standard, adopted in 1941 and refined for color in the , utilized a 60 Hz field refresh rate (approximately 59.94 Hz to avoid interference with audio carriers), delivering 30 frames per second through interlaced scanning. This was influenced by the 60 Hz grid in , ensuring stable synchronization without visible flicker. Conversely, in and parts of and , the PAL and standards, developed in the , employed a 50 Hz field refresh rate for 25 frames per second, matching the 50 Hz European to minimize hum bars and maintain picture stability. These origins persisted into , with ATSC in the retaining 60 Hz compatibility and in supporting 50 Hz signals. While streaming platforms often use 24, 30, or 60 FPS globally, traditional broadcast content adheres to regional standards, with 60 Hz in the (ATSC) and 50 Hz in / (DVB), though modern TVs support both via flexible processing. For instance, while core PAL broadcasts remain at 50 Hz, European HD and UHD content is typically produced at 50i or 50p to match regional standards, even as global platforms like and favor 60 FPS for some content. This is evident in the adoption of in the , which supports 60 Hz as the baseline, while DVB standards in 50 Hz regions maintain 50 Hz signals with support for frame rates like 50p. Smart TV panels in broadcast receivers, typically LCD or , feature native refresh rates of 60-120 Hz to handle these signals efficiently, with motion processing algorithms interpolating frames to achieve effective rates up to 240 Hz for reduced blur during fast-action content like sports. Transmission standards such as HDMI 2.1 and further enable high-refresh-rate broadcast handling, supporting up to 120 Hz at for dynamic content, while 8K televisions maintain a 60 Hz base to balance bandwidth demands. In regions with PAL heritage, upgrades to 100 Hz processing emerged in the and persist in some models to double the 50 Hz signal, improving motion smoothness particularly for soccer broadcasts where rapid panning benefits from reduced judder and flicker. As of 2025, HDR10+ Gaming certification for televisions mandates 120 Hz support with (VRR) at 4K, ensuring low-latency performance for interactive broadcast-enhanced gaming experiences.

Cinematic Content Reproduction

Cinematic films are typically produced at 24 frames per second (FPS), a standard originating from the era of projection to balance motion illusion and efficiency. When reproducing this content on television displays, which often operate at higher refresh rates like 60 Hz or 120 Hz, adaptations are necessary to map the source frames to the display's refresh cycles without introducing temporal artifacts. In legacy systems, converting 24 FPS to 60 fields per second (equivalent to 30 FPS interlaced) employs 3:2 pulldown, where each pair of frames is telecined into five fields: the first frame split into three fields and the second into two. This process ensures the total fields match over time but results in uneven frame durations, particularly noticeable as judder during panning shots, where horizontal motion appears stuttery due to inconsistent frame repetition. Modern televisions address these issues through modes, especially on 120 Hz panels, where the refresh rate is an multiple of 24 (120 ÷ 24 = 5), allowing each source frame to be repeated exactly five times without pulldown or judder. This matching preserves the original temporal cadence of cinematic content. Alternatively, frame interpolation techniques generate synthetic intermediate frames to upconvert 24 FPS to 60 or 120 FPS, reducing perceived judder by creating smoother motion; however, this often produces the " effect," an overly fluid appearance reminiscent of video shot at higher frame rates. While interpolation benefits fast-motion scenes by minimizing blur and stutter, it can alter the intended "filmic" aesthetic—characterized by subtle motion blur and a sense of weight in movement—that directors aim for at 24 FPS, leading purists to favor native 24 Hz playback modes to maintain artistic intent. Judder from rate mismatches can be quantified by the cycle length, determined using the (GCD) of the source FPS and refresh rate; specifically, the judder cycle spans refresh rategcd⁡(source FPS,refresh rate)\frac{\text{refresh rate}}{\gcd(\text{source FPS}, \text{refresh rate})} source frames, after which the repetition pattern repeats. For instance, displaying 24 FPS on a 60 Hz yields a cycle of 5 source frames (GCD=12, 60/12=5), manifesting the familiar 3:2 pattern. Standards for cinematic reproduction support native 24 FPS playback; Blu-ray discs encode movies at 23.976 FPS (precisely 24/1.001) to align with this format, enabling judder-free display on compatible systems. Streaming services like deliver cinematic titles at 24 FPS where possible, with output adjustable to 24 Hz via for optimal reproduction, though fallback to 60 Hz occurs in regions without native support.

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