origin of lag in lcd displays quotation

2023-01-03 12:32:11

Display lag is a phenomenon associated with most types of liquid crystal displays (LCDs) like smartphones and computers and nearly all types of high-definition televisions (HDTVs). It refers to latency, or lag between when the signal is sent to the display and when the display starts to show that signal. This lag time has been measured as high as 68 ms,Hz display. Display lag is not to be confused with pixel response time, which is the amount of time it takes for a pixel to change from one brightness value to another. Currently the majority of manufacturers quote the pixel response time, but neglect to report display lag.

For older analog cathode ray tube (CRT) technology, display lag is nearly zero, due to the nature of the technology, which does not have the ability to store image data before display. The picture signal is minimally processed internally, simply for demodulation from a radio-frequency (RF) carrier wave (for televisions), and then splitting into separate signals for the red, green, and blue electron guns, and for the timing of the vertical and horizontal sync. Image adjustments typically involve reshaping the signal waveform but without storage, so the image is written to the screen as fast as it is received, with only nanoseconds of delay for the signal to traverse the wiring inside the device from input to the screen.

For modern digital signals, significant computer processing power and memory storage is needed to prepare an input signal for display. For either over-the-air or cable TV, the same analog demodulation techniques are used, but after that, then the signal is converted to digital data, which must be decompressed using the MPEG codec, and rendered into an image bitmap stored in a frame buffer.

For progressive scan display modes, the signal processing stops here, and the frame buffer is immediately written to the display device. In its simplest form, this processing may take several microseconds to occur.

For interlaced video, additional processing is frequently applied to deinterlace the image and make it seem to be clearer or more detailed than it actually is. This is done by storing several interlaced frames and then applying algorithms to determine areas of motion and stillness, and to either merge interlaced frames for smoothing or extrapolate where pixels are in motion, the resulting calculated frame buffer is then written to the display device.

De-interlacing imposes a delay that can be no shorter than the number of frames being stored for reference, plus an additional variable period for calculating the resulting extrapolated frame buffer; delays of 16-32ms are common.

While the pixel response time of the display is usually listed in the monitor"s specifications, no manufacturers advertise the display lag of their displays, likely because the trend has been to increase display lag as manufacturers find more ways to process input at the display level before it is shown. Possible culprits are the processing overhead of HDCP, Digital Rights Management (DRM), and also DSP techniques employed to reduce the effects of ghosting – and the cause may vary depending on the model of display. Investigations have been performed by several technology-related websites, some of which are listed at the bottom of this article.

LCD, plasma, and DLP displays, unlike CRTs, have a native resolution. That is, they have a fixed grid of pixels on the screen that show the image sharpest when running at the native resolution (so nothing has to be scaled full-size which blurs the image). In order to display non-native resolutions, such displays must use video scalers, which are built into most modern monitors. As an example, a display that has a native resolution of 1600x1200 being provided a signal of 640x480 must scale width and height by 2.5x to display the image provided by the computer on the native pixels. In order to do this, while producing as few artifacts as possible, advanced signal processing is required, which can be a source of introduced latency. Interlaced video signals such as 480i and 1080i require a deinterlacing step that adds lag. Anecdotallyprogressive scanning mode. External devices have also been shown to reduce overall latency by providing faster image-space resizing algorithms than those present in the LCD screen.

Many LCDs also use a technology called "overdrive" which buffers several frames ahead and processes the image to reduce blurring and streaks left by ghosting. The effect is that everything is displayed on the screen several frames after it was transmitted by the video source.

Display lag can be measured using a test device such as the Video Signal Input Lag Tester. Despite its name, the device cannot independently measure input lag. It can only measure input lag and response time together.

Lacking a measurement device, measurement can be performed using a test display (the display being measured), a control display (usually a CRT) that would ideally have negligible display lag, a computer capable of mirroring an output to the two displays, stopwatch software, and a high-speed camera pointed at the two displays running the stopwatch program. The lag time is measured by taking a photograph of the displays running the stopwatch software, then subtracting the two times on the displays in the photograph. This method only measures the difference in display lag between two displays and cannot determine the absolute display lag of a single display. CRTs are preferable to use as a control display because their display lag is typically negligible. However, video mirroring does not guarantee that the same image will be sent to each display at the same point in time.

In the past it was seen as common knowledge that the results of this test were exact as they seemed to be easily reproducible, even when the displays were plugged into different ports and different cards, which suggested that the effect is attributable to the display and not the computer system. An in depth analysis that has been released on the German website Prad.de revealed that these assumptions have been wrong. Averaging measurements as described above lead to comparable results because they include the same amount of systematic errors. As seen on different monitor reviews the so determined values for the display lag for the very same monitor model differ by margins up to 16 ms or even more.

To minimize the effects of asynchronous display outputs (the points of time an image is transferred to each monitor is different or the actual used frequency for each monitor is different) a highly specialized software application called SMTT

Display lag contributes to the overall latency in the interface chain of the user"s inputs (mouse, keyboard, etc.) to the graphics card to the monitor. Depending on the monitor, display lag times between 10-68 ms have been measured. However, the effects of the delay on the user depend on each user"s own sensitivity to it.

Display lag is most noticeable in games (especially older video-game consoles), with different games affecting the perception of delay. For instance, in PvE, a slight input delay is not as critical compared to PvP, or to other games favoring quick reflexes like

If the game"s controller produces additional feedback (rumble, the Wii Remote"s speaker, etc.), then the display lag will cause this feedback to not accurately match up with the visuals on-screen, possibly causing extra disorientation (e.g. feeling the controller rumble a split second before a crash into a wall).

TV viewers can be affected as well. If a home theater receiver with external speakers is used, then the display lag causes the audio to be heard earlier than the picture is seen. "Early" audio is more jarring than "late" audio. Many home-theater receivers have a manual audio-delay adjustment which can be set to compensate for display latency.

Many televisions, scalers and other consumer-display devices now offer what is often called a "game mode" in which the extensive preprocessing responsible for additional lag is specifically sacrificed to decrease, but not eliminate, latency. While typically intended for videogame consoles, this feature is also useful for other interactive applications. Similar options have long been available on home audio hardware and modems for the same reason. Connection through VGA cable or component should eliminate perceivable input lag on many TVs even if they already have a game mode. Advanced post-processing is non existent on analog connection and the signal traverses without delay.

A television may have a picture mode that reduces display lag for computers. Some Samsung and LG televisions automatically reduce lag for a specific input port if the user renames the port to "PC".

LCD screens with a high response-time value often do not give satisfactory experience when viewing fast-moving images (they often leave streaks or blur; called ghosting). But an LCD screen with both high response time and significant display lag is unsuitable for playing fast-paced computer games or performing fast high-accuracy operations on the screen, due to the mouse cursor lagging behind.

origin of lag in lcd displays quotation

One of the areas where the A-MVA panel does extremely well is in the areas of display lag and pixel response time. Just to recap, you may have heard complaints about "input lag" on various LCDs, so that"s one area we look at in our LCD reviews. We put input lag in quotation marks because while many people call it "input lag", the reality is that this lag occurs somewhere within the LCD panel circuitry, or perhaps even at the level of the liquid crystals. Where this lag occurs isn"t the concern; instead, we just want to measure the duration of the lag. That"s why we prefer to call it "processing lag" or "display lag".

To test for display lag, we run the Wings of Fury benchmark in 3DMark03, with the output set to the native LCD resolution - in this case 1920x1200. Our test system is a quad-core Q6600 running a Radeon HD 3870 on a Gigabyte GA-X38-DQ6 motherboard - we had to disable CrossFire support in order to output the content to both displays. We connect the test LCD and a reference LCD to two outputs from the Radeon 3870 and set the monitors to run in clone mode.

The reference Monitor is an HP LP3065, which we have found to be one of the best LCDs we currently possess in terms of not having display lag. (The lack of a built-in scaler probably has something to do with this.) While we know some of you would like us to compare performance to a CRT, that"s not something we have around our offices anymore. Instead, we are looking at relative performance, and it"s possible that the HP LP3065 has 20ms of lag compared to a good CRT - or maybe not. Either way, the relative lag is constant, so even if a CRT is faster at updating, we can at least see if an LCD is equal to or better than our reference display.

While the benchmark is looping, we snap a bunch of pictures of the two LCDs sitting side-by-side (using a relatively fast shutter speed). 3DMark03 shows the runtime with a resolution of 10ms at the bottom of the display, and we can use this to estimate whether a particular LCD has more or less processing lag than our reference LCD. We sort through the images and discard any where the times shown on the LCDs are not clearly legible, until we are left with 10 images for each test LCD. We record the difference in time relative to the HP LP3065 and average the 10 results to come up with an estimated processing lag value, with lower numbers being better. Negative numbers indicate a display is faster than the HP LP3065, while positive numbers mean the HP is faster and has less lag.

It"s important to note that this is merely an estimate - whatever the reference monitor happens to be, there are some inherent limitations. For one, LCDs only refresh their display 60 times per second, so we cannot specifically measure anything less than approximately 17ms with 100% accuracy. Second, the two LCDs can have mismatched vertical synchronizations, so it"s entirely possible to end up with a one frame difference on the time readout because of this. That"s why we average the results of 10 images, and we are confident that our test procedure can at least show when there is a consistent lag/internal processing delay. Here is a summary of our results for the displays we have tested so far.

As you can see, all of the S-PVA panels we have tested to date show a significant amount of input lag, ranging from 20ms up to 40ms. In contrast, the TN and S-IPS panels show little to no processing lag (relative to the HP LP3065). The BenQ FP241VW performs similarly to the TN and IPS panels, with an average display lag of 2ms - not something you would actually notice compared to other LCDs. Obviously, if you"re concerned with display lag at all, you"ll want to avoid S-PVA panels for the time being. That"s unfortunate, considering S-PVA panels perform very well in other areas.

Despite what the manufacturers might advertise as their average pixel response time, we found most of the LCDs are basically equal in this area - they all show roughly a one frame "lag", which equates to a response time of around 16ms. In our experience, processing lag is far more of a concern than pixel response times. Taking a closer look at just the FP241VW, we can see the typical one frame lag in terms of pixel response time. However, the panel does appear to be a little faster in response time than some of the other panels we"ve tested (notice how the "ghost image" isn"t as visible as on the HP LP3065), and we didn"t see parts of three frames in any of the test images.

After the initial article went live, one of our readers who works in the display industry sent me an email. He provides some interesting information about the causes of image lag. Below is an (edited) excerpt from his email. (He wished to remain anonymous.)

PVA and MVA have inherent drawbacks with respect to LCD response time, especially gray-to-gray. To address this shortcoming, companies have invested in ASICs that perform a trick generically referred to as "overshoot." The liquid crystal (LC) material in *VA responds sluggishly to small voltage changes (a change from one gray level to another). To fix this, the ASIC does some image processing and basically applies an overvoltage to the electrodes of the affected pixel to spur the LC material into rapid movement. Eventually the correct settling voltage is applied to hold the pixel at the required level matching the input drive level.

It"s very complicated math taking place in the ASIC in real time. It works well but with an important caveat: it requires a frame buffer. What this means is that as video comes into the panel, there is a memory device that can capture one whole video frame and hold it. After comparing it to the next incoming frame, the required overshoot calculations are made. Only then is the first captured frame released to the panel"s timing controller, which is when the frame is rendered to the screen. As you may have already guessed, that causes at least one frame time worth of lag (17ms).

Some companies discovered some unintended artifacts in their overshoot calculations and the only way they saw to correct these was to allow for their algorithm to look ahead by two frames instead of one. So they had to up the memory of the frame buffer and now they started capturing and holding not one but two frames upon which they make their complex overshoot predictions to apply the corrected pixel drive levels and reduce gray-to-gray response time (at the expense of lag time). Again, it works very well for improving response time, but at the expense of causing lag, which gamers hate. That in a nutshell is the basis of around 33ms of the lag measured with S-PVA.

Not every display uses this approach, but this could account for the increase in display lag between earlier S-PVA and later S-PVA panels. It"s also important to note that I tested the Dell 2408WFP revision A00, and apparently revision A01 does not have as much lag. I have not been able to confirm this personally, however. The above also suggest that displays designed to provide a higher image quality through various signal processing techniques could end up with more display lag caused by the microchip and microcode, which makes sense. Now all we need are better algorithms and technologies in order to reduce the need for all of this extra image processing -- or as we have seen with some displays (particularly HDTVs), the ability to disable the image processing.

origin of lag in lcd displays quotation

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origin of lag in lcd displays quotation

Display lag is a phenomenon associated with some types of LCD displays, and nearly all types of HDTVs, that refers to latency, or lag measured by the difference between the time a signal is input into a display and the time it is shown by the display. This lag time has been measured as high as 68ms, or the equivalent of 3-4 frames on a 60 Hz display. Display lag is not to be confused with pixel response time.

For older analog cathode ray tube technology, display lag is extremely low due to the nature of the technology which does not have the ability to store image data before display. The picture signal is minimally processed internally, simply for demodulation from a radio frequency carrier wave (for televisions), and then splitting into separate signals for the red, green, and blue electron guns, and for timing of the vertical and horizontal sync. Image adjustments typically involved reshaping the signal waveform but without storage, so the image is written to the screen as fast as it is received, with only nanoseconds of delay for the signal to traverse the wiring inside the device from input to the screen.

For modern digital signals, significant computer processing power and memory storage is needed to prepare an input signal for display. For over-the-air or cable-TV, the same analog demodulation techniques are used, but after that the signal is converted to digital data which must be decompressed using the MPEG codec, and rendered into an image bitmap stored in a frame buffer. This frame buffer is then procedurally written to the display device. In its simplest form this processing may take several microseconds to occur.

While the pixel response time of the display is usually listed in the monitor"s specifications, no manufacturers advertise the display lag of their displays, likely because the trend has been to increase display lag as manufacturers find more ways to process input at the display level before it is shown. Possible culprits are the processing overhead of HDCP, DRM, and also DSP techniques employed to reduce the effects of ghosting - and the cause may vary depending on the model of display. Investigations have been performed by several technology related websites; some of which are listed at the bottom of this article.

LCD, plasma, and DLP displays, unlike CRTs, have a native resolution. That is, they have a fixed grid of pixels on the screen that show the image sharpest when running at the native resolution (so nothing has to be scaled full-size which blurs the image). In order to display non-native resolutions, such displays must use video scalers, which are built into most modern monitors. As an example, a display that has a native resolution of 1600x1200 being provided a signal of 640x480 must scale width and height by 2.5x to display the image provided by the computer on the native pixels. In order to do this while producing as few artifacts as possible, advanced signal processing is required, which can be a source of introduced latency. Interlaced video signals such as 480i and 1080i require a deinterlacing step that adds lag. Anecdotally, display lag is significantly less when displays operate in native resolutions for a given LCD screen and in a progressive scanning mode. External devices have also been shown to reduce overall latency by providing faster image-space resizing algorithms than those present in the LCD screen.

Showing the existence of input lag requires a test display (the display being measured), a control display (usually a CRT) that would ideally have no display lag, a computer capable of mirroring output to two displays, stopwatch software, and a high-speed camera pointed at the two displays running the stopwatch program. The lag time is measured by taking a photograph of the displays running the stopwatch software, then subtracting the two times on the displays in the photograph. This method only measures the difference in display lag between two displays and cannot determine the absolute display lag of a single display. CRTs are preferable to use as a control display because their display lag is typically negligible. Also, video mirroring does not guarantee that the same image will be sent to each display at the same point in time.

Several approaches to measure display lag have been restarted in slightly changed ways but still reintroduced old problems, that have already been solved by the former mentioned SMTT. One such method involves connecting a laptop to an HDTV through a composite connection and run a timecode that shows on the laptop"s screen and the HDTV simultaneously and recording both screens with a separate video recorder. When the video of both screens is paused, the difference in time shown on both displays have been interpreted as an estimation for the display lag. Nevertheless this is almost identical to the use of casual stopwatches on two monitors using a "clone view" monitor setup as it does not care about the missing synchronisation between the composite video signal and the display of the laptop"s screen or the display lag of that screen or the detail that the vertical screen refresh of the two monitors is still asynchronous and not linked to each other. Even if v-sync is activated in the driver of the graphics card the video signals of the analog and the digital output will not be synchronized. Therefore it is impossible to use a single stop watch for display lag measurements, nervertheless if it is created by a timecode or a simple stopwatch application, as it will always cause an error of up to 16 ms or even more.

Display lag contributes to the overall latency in the interface chain of the user"s inputs (mouse, keyboard, etc.) to the graphics card to the monitor. Depending on the monitor, display lag times between 10ms and 68ms have been measured. However, the effects of the delay on the user depend on the user"s own sensitivity to it.

Display lag is most noticeable in games (especially older video game consoles), with different games affecting the perception of delay. For instance, in World of Warcraft"s PvE, a slight input delay isn"t as critical compared to PvP, or to games favoring quick reflexes like Counter-Strike. Rhythm based games such as Guitar Hero also require exact timing; display lag will create a noticeable offset between the music and the on-screen prompts. Notably, many games of this type include an option that attempts to calibrate for display lag. Arguably, fighting games such as Street Fighter and Tekken are the most affected, since they may require move inputs within extremely tight windows that sometimes only last 1-3 frames on screen.

TV viewers can be affected as well. If a home theater receiver with external speakers is used then the display lag causes the audio to be heard earlier than the picture is seen. "Early" audio is more jarring than "late" audio. Many home theater receivers have a manual audio delay adjustment which can be set to compensate for display latency.

Many televisions, scalers and other consumer display devices now offer what is often called a "game mode," in which the extensive preprocessing responsible for additional lag is specifically sacrificed to decrease, but not eliminate, latency. While typically intended for videogame consoles, this feature is also useful for other interactive applications. Similar options have long been available on home audio hardware and modems for the same reason.

LCD screens with a high response time value often do not give satisfactory experience when viewing fast moving images (They often leave streaks or blur; called ghosting). But an LCD screen with both high response time and significant display lag is unsuitable for playing fast paced computer games or performing fast high accuracy operations on the screen due to the mouse cursor lagging behind. Manufacturers only state the response time of their displays and do not inform customers of the display lag value.

The process that occurs from when the user presses a button to when the screen reacts is outlined below (steps which have negligible response time contributions have been omitted). Each step in the process adds response time (commonly known as "input lag"), which varies from minor to noticeable.

1: Controller sends signal to console For wired controllers, this lag is negligible. For wireless controllers, opinions vary as to the effect of this lag. It is likely that opinions vary due to each user"s sensitivity to lag, model of wireless controller and the other equipment in the signal chain (i.e. the rest of their gaming setup).

2: Network lag (online gaming only) Since the console must know the current location of other players, there is sometimes a delay as this information travels over the network. This occurs in games where the input signals are "held" for several frames (to allow time for the data to arrive at every player"s console) before being used to render the next frame. At 25 FPS, holding 4 frames adds 40ms to the overall input lag.

3: Console processes information and sends frame output to television A console will send out a new frame once it has finished processing it. This is measured with the frame rate. Using Gran Turismo 5 as an example, the maximum theoretical framerate is 60 FPS (frames per second), which means the minimum theoretical input lag for the overall system is 17ms (note: the maximum real world FPS in 3D mode is 40-50 FPS). In situations where processor load is high (e.g. many cars are on-screen on a wet track), this can drop to 30 FPS (16 FPS for 3D mode) which is equivalent to 32ms.

4: Television processes frame (image correction, upscaling, etc.) and pixel changes colour This is the "input lag" of the television. Image processing (such as upscaling, 100 Hz, motion smoothing, edge smoothing) takes time and therefore adds some degree of input lag. It is generally considered that input lag of a television below 30ms is not noticeable, discussions on gaming forums tend to agree with this value. Once the frame has been processed, the final step is the pixel response time for the pixel to display the correct colour for the new frame.

Typical overall response times Overall response times (from controller input to display response) have been conducted in these tests: http://www.eurogamer.net/articles/digitalfoundry-lag-factor-article?page=2 It appears that overall input lag times of approximately 200ms are distracting to the gamer. It also appears that (excluding television input lag) 133ms is an average response time and the most sensitive games (first person shooters and Guitar Hero) achieve response times of 67ms (again, excluding television input lag).

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origin of lag in lcd displays quotation

For PC monitors and smart TVs, speed largely comes down to pixel response and input lag. They’re both measured in milliseconds, and they’re at least a little interrelated – but they’re not the same thing at all.

First let’s establish the basics. In simple terms, response time (or "pixel response") describes the time taken for a display to change the colour of any given pixel, millions of which make up the overall image. Really broadly, pixel response is all about the look of a display. With a fast response time, moving images will be sharp and clear as opposed to blurry and smeared.

As for input lag, that’s a measure of the delay between signal output from a source device, such as a games console, set top box or PC, and the video image being shown on the display. And it’s all about feel. Does the screen respond quickly to your control inputs in a game? If it does, it has low lag or latency. If there’s a noticeable delay between wiggling a mouse or control pad and on-screen movement, then it probably suffers from significant lag.

Anyway, response and lag don’t apply in quite the same way to all display and panel types, be that OLED vs LCD or TVs and PC monitors (note that TVs and other screens marketed as ‘LED’ are typically LCD panels with LED backlights, not actually LED panels).

How is response time / pixel response measured and what do the numbers really mean? The most common metric of pixel response is known as grey-to-grey, sometimes abbreviated to GtG. As the name implies, it’s not a measure of the time taken for a pixel to fully transition from off to on or from black to white. Instead, GtG pixel response records the time taken to move between two intermediate colors.

What’s more, the industry standard VESA method for measuring GtG response doesn’t even record the full time taken for that intermediate transition. It actually discards the first 10% and last 10% of the transition, recording only the time taken for the middle 80%.

Shown on a graph, the pixel response of an LCD panel follows an ‘S’ curve, with a slightly sluggish immediate response, followed by that rapid middle phase, before response tails off dramatically towards the end of the transition. The net result is the time taken to fully transition from one color to another can be dramatically longer than the quoted GtG response.

There is another measure of pixel response known as MPRT or ‘moving picture response time’. It’s intended to be a better measure of actual perceived blurring based on the abilities of the human eye.

In theory, MPRT response is a direct function of refresh rate. So, a refresh rate of 1000Hz is required to achieve a 1ms MPRT pixel response. However, mitigating measures including black-frame insertion or strobing backlights can improve MPRT response to below the refresh rate of the panel and to the point where it’s typically faster than a screen’s GtG response, at least in terms of quoted specifications.

That achievement, however, comes with several caveats. For starters, those mitigating measures usually don’t work when variable refresh rate or frame synching is enabled. Moreover, screen modes intended to improve MPRT response tend to reduce vibrancy and visual punch. So, it’s often not possible with a given display to achieve the best available MPRT response while maintaining optimal performance in other regards.

The fastest current LCD panels are quoted at 1ms for GtG response and 0.5ms for MPRT response. But independent testing shows a whole different ballgame. Sources including Rtings.com and Linus Tech Tips peg full-transition pixel response from speedy OLED sets like LG C1 and CX panels at around two to three milliseconds, with the bulk of the transition (and thus the GtG equivalent performance) completed in a fraction of a millisecond.

Results for LCD technology vary a little more, probably due to methodology. But the best case scenario for an ultra-fast-IPS LCD monitor, such as the Asus ROG Swift 360Hz PG259QN, by comparison, is around 3ms for the bulk of the transition and 6ms for the full color change while other results push those two metrics out to 6ms and 10ms or more respectively. Either way, OLED is clearly faster.

The refresh rate of a screen puts a hard limit on the minimum latency or input lag it can achieve. To put some numbers on that, most mainstream monitors and TVs refresh at 60Hz or once every 16.67ms. Increase the refresh rate to 120Hz and the screen updates every 8.33ms.

In the PC gaming monitor market, refresh rates up to 360Hz are now available, translating into a new frame every 2.7ms (TVs can be a bit more complicated due to technologies like frame insertion and motion smoothing, though).

To understand why that matters, imagine for a moment playing a game with a refresh rate of just 1Hz – rather than the 60Hz or 120Hz found on a decent gaming TV. Yes, it would be absolutely horrible in terms of rendering smoothness. But you could wiggle your mouse or controller pad around for a full second and get absolutely no response on the screen. Nightmare.Running outside of game mode, the LG C1 is tragically slow at nearly 90ms, which neatly demonstrates just how much impact image processing can have.

Now, 16.67ms might not sound like a long time to wait – but should the screen require any time at all to process the signal, that latency will only increase, as those 16.67ms are also just the latency generated by your display. A PC or games console needs time to process a control input, feed it through the game engine and kick out frames in response. It all adds up.

The other part of the equation is image processing. Until quite recently, that could be death for TVs, because most sets heavily process video by default to adjust and (theoretically) improve the image, whereas PC monitors tend to run with minimal tweaks.

Happily, some TVs now offer a dedicated low-latency game mode with minimal processing. Such TVs tend to be comparable to monitors running at the same refresh rate in terms of lag. The LG C1 OLED TV has been measured as low as 5ms at 120Hz. Intriguingly, running outside of game mode, the C1 is tragically slow at nearly 90ms, which neatly demonstrates just how much impact image processing can have.

In terms of refresh rate, the fastest current PC monitors can hit 360Hz, while the highest refresh TV sets accept an input signal of 120Hz. Some TVs have higher internal refresh rates of 240Hz or more, but in terms of latency or input lag, it’s the signal refresh from the source device that matters.

Long story short, the fastest OLED TVs deliver as little as 5ms of lag, while the quickest PC monitors including the aforementioned Asus panel along with other 360Hz monitors such as the Alienware AW2521H have been clocked at well under 2ms. So while OLED wins out on pixel response, certain LCD monitors have an advantage with input lag.

For OLED TVs, it’s pretty simple. You need a modern set with true 120Hz refresh and a low-latency game mode. For now, there’s simply nothing faster in that market. Pixel response from such displays is beyond reproach, delivering a super crisp, sharp image. In fact, any blurring will largely be a consequence of the limitations of human vision. For latency, 120Hz 4K TVs with OLED are pretty darn good. For most gamers, they’ll feel very slick and responsive. But serious esports players may appreciate something a little bit quicker.

Apart from the differences discussed between GtG response and MPRT, IPS and VA panel types tend not to be entirely comparable. By that we mean that the subjective experience of a 1ms IPS panel is usually that little bit crisper, clearer and cleaner in terms of response than a VA panel. IPS, in short, tends to be faster.

What’s more, pretty much all gaming monitors offer user-configurable overdrive which can accelerate response but also introduce unwanted image quality issues such as overshoot and inverse ghosting. All those caveats aside, the latest 1ms IPS panels deliver the best performance with very low levels of blur, while 1ms VA monitors are just a little behind. The next rung down and probably the slowest you should consider for gaming is 4ms. Depending on the monitor in question, the panel type and the settings used, such screens may not differ that greatly in terms of the subjective experience. But the worst of them will have noticeably more blur than a 1ms display.

Beyond that, you’re into 7ms and beyond territory. On paper, that ought to be fine. But as we’ve seen, even the fastest LCD panels rated at 1ms can be measured at 10 times that long for real-world response. So quoted specifications should be viewed more as a tool with which to categorize screens than set expectations for actual performance.

But what of lag or latency? Most gamers will find a PC monitor with 144Hz refresh offers no noticeable lag and feels seriously slick and super quick. For really competitive esports competition there are small gains to be had from 240Hz and 360Hz displays. But for us? We’d be very happy with either a 120Hz OLED TV or a 144Hz 1ms monitor.Just want a good low-lag screen? Check out the best gaming monitors and best 120Hz TVsToday"s best gaming monitors and 120Hz TVs

origin of lag in lcd displays quotation

As a scientist, you need to know the advantages and limitations of the technology you use, and understand which features really affect the quality of your stimulus. There are no secrets to Cambridge Research Systems" products - just good engineering, which we are happy to explain. If you don"t find the answers you"re looking for here, please drop us an email.

Most MR Safe monitors were originally designed for TV or PC use, and will lag behind the input signal by many frames, in an uncontrolled way. But timing can be crucial in scientific applications. BOLDscreens are designed to deliver your video signal directly to the screen. There is a very small fixed delay equal to just one horizontal line (~100 microseconds).

The 23” display provides a reasonable field of view for a 60cm bore. BOLDscreen 23 is designed to be placed in close proximity to the viewer right at the exit of the bore of the scanner. This keeps the viewing distance is as short as possible - about 1m. Since viewing distance dramatically affects the field of view, BOLDscreen 23 can often achieve a larger field of view than bigger monitors with longer viewing distance. If you want a bigger monitor or have a 70cm bore, consider the larger BOLDscreen 32 design.

Scaling and resampling by the stimulus monitor is highly undesireable, as it changes your stimulus and timing in uncontrolled ways. BOLDscreen is purposefully designed with no image processing circuitry, so that unlike other monitors, you can be sure that what you put in is what you get out. If you need to scale you image, we recommend using your computer"s graphics card.

Some manufacturers quote high contrast figures which compare white versus black with the screen switched off. We don"t think that"s a useful measurement, as the screen is not switched off when you"re presenting stimuli! We measure the contrast between the emitted light though the panel with the pixels set to white versus set to black with the same backlight intensity – what you see in actual use. Measured in this way, BOLDscreen 23 has a typical contrast ratio of 800:1, similar to most high quality LCD displays.

Yes. We designed BOLDscreen 23 without physical buttons, as they can cause electromagnetic interference, and are susceptible to accidental changes! Instead, all settings are easily configured on a removable SD card.

The mirror mode feature allows you to automatically left/right flip your image when your subject is viewing the display via a single mirror, without the requirement to manually adjust your stimuli.

We provide a 20m single link DVI fibre optic cable with each BOLDscreen 23 display. This is passed through the waveguide into the control room and connected to your host computer DVI output. The cable has integrated transmitter and receiver elements, so there"s no chance of them getting lost.

We are the only manufacturer and vendor that provides a MR Safe LCD monitor that you can site anywhere inside the MRI room, even directly at the exit of the rear of the magnet bore so that you can maximise the visual field of view.

BOLDscreen 23 has no observed effect on functional and structural MRI scans at 3T, even when located at directly at the exit of scanner bore, and no effect on displayed image whilst scanning.

BOLDscreen 23 is constructed mostly from aluminium, 316 stainless steel, glass and plastic. These materials are non-magnetic. There is a very small amount of ferro-magnetic content due mainly to nickel plating on some miniature electronic components, and some tiny ferrite components. This content is of the order of a few grammes in a total monitor mass of about 10kg. The BOLDscreen electronics have been designed to work in the high magnetic field (it is not just a normal LCD monitor in a screened box). There is therefore no electrical hazard from operating BOLDscreen 23 in the magnetic field of any field strength. The display is MR Safe, and the power supply and cables are MR Conditional, as defined by ASTM F2503-08.

We want all of our customers to be very happy with the equipment we supply. Please contact us to discuss your requirements, and we will help you to assess whether BOLDscreen 23 or another one of our BOLDscreen monitors is the best solution for your research.

If you"re still not sure, ask us for a 60 day trial: you place an order for BOLDscreen 23 in the normal way, then you have 60 days to try it out with your scanner, with the option to cancel if you decide that it"s unsuitable in any way.

origin of lag in lcd displays quotation

While both input lag and response time are equally important for a fluid gaming experience, too high input lag can make competitive gaming unbearable.

Now, the specified pixel response time speed that monitor manufacturers quote (such as 1ms GtG, 4ms GtG, etc.) refers to the display’s fastest pixel transition possible from one shade of gray to another under certain testing conditions – it’s not the average speed.

Pixels take longer to change from black to white than vice versa, so even if all white to black pixel transitions are below the quoted 4ms on a 144Hz monitor, for instance, some dark to light pixel transitions still might take over 10ms.

Consequently, you would get noticeable black smearing in fast-paced scenes with a lot of dark pixels involved, while in other scenes, ghosting wouldn’t be as noticeable.

Generally, if you want to avoid ghosting, you should look for gaming monitors with a specified response time speed of 1ms GtG (Gray to Gray) – or lower.

Inverse ghosting is characterized as a bright trail following moving objects, which is caused by pixels being pushed too hard via an aggressive overdrive setting.

To find out just how well the overdrive is implemented on a monitor, as well as what setting should be used at which refresh rate, you will need to look for detailed monitor reviews.

Sometimes, monitor manufacturers will specify a response time speed of 1ms without declaring if it’s a GtG or MPRT (Moving Picture Response Time) measure.

The 1ms MPRT measure refers to the backlight strobing technology of the monitor, which reduces the perceived motion blur at a cost of picture brightness.

So, a 120Hz display will have essentially half the input lag in comparison to a 60Hz display since the picture gets updated more frequently and you can react to it sooner.

Pretty much all new high refresh rate gaming monitors have low enough input lag in relation to their refresh rate that the delay between your actions and the result on the screen will be imperceptible.

Therefore, if you want the fastest 240Hz or 360Hz gaming monitor available for competitive gaming, you should focus on its response time speed performance.

origin of lag in lcd displays quotation

Most computer engineers would define a display’s input lag as being the difference in time between the output from a graphics card, to the time that image is displayed on the screen. There are other factors which constitute “lag” which we will discuss on this page, and which ones you should be the most concerned about when looking to purchase a display or device for gaming.

It is worth noting that the display tests measure a different type of lag than the peripheral devices tests, and that the phrase “Input Lag” has no actual defined measurement by computer scientists. Display input lag is concerned with the time required for the pixels to show an image after it has been processed and sent by the graphics card. This is different than the manufacturers quoted pixel responsiveness time (such as GTG response time, or BTW – more on this in a bit), which measures how quickly the pixels can change from one color to another. Pixel response times are what affect things like motion blurring and ghosting – which also an important measure for gamers needing maximum performance for fast paced games.

The amount of lag varies greatly depending on the display, hence why there is a noted difference between manufacturers gaming displays vs their normal ones for casual/business use. It’s become commonplace for manufacturers to focus on gaming displays to provide the fastest response times and lowest input lag possible for the type of panel being used. The difference in lag depends on the internals of a monitor, such as its internal circuit board and scaling chips, which determine its signal processing time and therefore its quoted input lag and responsiveness. Many manufacturers take active measures for their gaming displays to reduce input lag as much as possible, with many offering modes which can bypass the scaling chips and including other options to reduce the input lag.

Short answer:input lag is caused by a combination of two things – the signal processing delay caused by the monitor’s internal electronic board, and the response time of the pixels.

“Input Lag” is made up of 2 parts. When a signal is sent from the GPU to a screen, the instant it hits the port on the back of the monitor/TV it begins what we would define as “Input Lag”. As the signal enters the display, it has 2 sections of lag, which can be measured.

Pixel Responsiveness Lag (The lag from the time is takes for the pixels to change to show the image after it was processed by the monitor’s internal circuit board).

Because the quoted pixel responsiveness time provided by the manufacturer is usually found to be pretty accurate (after comparing our tests to their quoted times), on InputLag.com we only focus on reporting this number.

Poor) A lag of more than 66.6ms / more than 2 frames at 30Hz – Very noticeable/distracting lag. Early LCD’s from the 1990’s may be this bad, but they do not exist now.

I think you see the pattern here. 1 second = 1000 milliseconds. So, if a monitor is displaying a game at 144 frames per second, you can do the math to determine what an acceptable frame loss should be.

If the monitor has one frame of lag, it won’t really be noticeable because there are 144 frames being shown every second. However, a monitor running at only 30 FPS, skipping one frame constantly from the input lag is going to be much more noticeable, and put you at a significant disadvantage.

There are a few main reasons for this, most notably is the lack of testing ability for higher framerates. Leo’s tool is limited to 1080p and 60Hz, while many of the top gaming monitors are way ahead of this, pushing 240Hz nowadays. It would not be accurate to be testing an expensive top-shelf gaming monitor with a native 240Hz refresh rate, with a tool that can only measure up to 60Hz. It forces you to measure the input lag of that 240Hz monitor at only 60Hz, which means the fastest it can possibly score is 16.67ms. Wait, what – the maximum visible display lag for 60Hz is 16.67ms? Yes.

For instance, if a 240Hz monitor is rated as “Excellent @240Hz”, it will still be rated “Excellent” at 60Hz. The refresh rate of a monitor has a direct impact on its input lag. A 60Hz monitor, for example, will never have a visible input lag below 16.67ms, because at 60Hz, the screen gets refreshed every 16.67ms (refresh to the bottom of the screen, see the next question for an explanation). So, if the overall input lag time is really 15ms, it doesn’t matter, because the lag time is less than the time for the screen to refresh the image, and it can’t be visibly measured. A 120Hz display halves that time to 8.3ms, and a 240Hz display further reduces it to 4.17ms.

This is a huge distinction that needs to be made. The web is full of misinformation concerning quoted “Input Lag” times, which often are only measuring the time it takes for the pixels to change from black to white, and is more of an indication of pixel response time rather than the true “input lag” that gamers are wanting to know for an advantage.

Should Leo Bodnar ever update a testing tool aimed at TV’s and Monitors, complete with support for 240Hz readings, and fixes the mentioned problems with his tool, we would be one of his first customers.

This is important to understand to get a good grasp of how monitors work and why there is always a difference in reported lag times. It also explains how some sites can quote an Input Lag time that is faster than the possible refresh time of the screen. LCD monitors refresh from top to bottom as seen below in the video.

Most people using Leo’s tool test the monitor and report the number from the middle of the screen, something that SMTT does as well. This is why the maximum visible display lag for 60Hz is 16.67ms, yet often gets reported as being lower for gaming displays running at 60Hz. If you test a 60Hz display with an exact quoted input lag time of 16.67ms (time to refresh to the last pixels at the bottom of the LCD panel), it should take roughly (just an estimate) 16.67ms/2 = 8.335ms to provide a reading in the middle of the display.

Output from Mouse/Keyboard/Controller -> Signal processed by Computer and Game -> Signal sent out to screen through HDMI/other cable (about 1/100th the speed of light [scienceline.ucsb.edu/getkey.php?key=2910]) -> monitor processes signal and sends to panel for display -> pixels on panel change to show image as intended.

What is highlighted in red is what we are measuring for the “Input Lag” of a display (TVs & Monitors). By using a tool to measure the screen going from white to black, it can only visibly measure

What is highlighted in green is what we have the least amount of control over, it’s up to your gaming computer/console to determine how quickly the signal gets processed. See here for more info.

What is highlighted in blue is what I consider to be Physical Input Lag – the time it takes for your mouse/keyboard/controller to send the signal to your computer. There is significant room for variation here, hence why this category is also so important to gaming.

Simply put, GTG is a more realistic representation of what the pixels will be like under normal gaming conditions. Grey is a unique color from a technical perspective. It’s half white, and half black – meaning the pixels have all of their colors activated to some degree from one frame to the next. That differs from BTW, which tests the time it takes for all the colors to become active (white) from them not being activated (black).

The SMTT tool provides the ability to test any 2 colors responsiveness times as well, such as blue to green. This is a decently realistic representation of responsiveness when compared to BTW, but GTG still wins for measuring responsiveness for real world play. Think about any game you enjoy playing, and take 1 frame of it (pause the game) and look at all the pixel colors. Most likely, it will be a wash of different colors, even for dark games. But when you dive further into what colors are actually being shown, most of them are much grayer than you would think. Download a tool such as Digital Color Meter (comes with all Macs), or Digital Colorimeter for Windows, and pick different pixels of that frame to see for yourself. Even on brightly colored animated games, like South Park or something from Nintendo, the “bright” colors you see are nowhere near as vibrant as what the pixel can actually go. It’s this distinction that needs to be made.

When you are testing BTW responsiveness, the white you see is all of the colors activated 100%, and with black, the colors are activated 0% – with the backlight on for both, of course. This is a good test, but it’s not really something that you will experience often while gaming, (unless you are playing a strobe light game or something).

When you are testing GTG responsiveness, you are going between 2 different shades of grey – usually going from colors being activated 40% to 60%, or 33% to 66%. This produces a more realistic test of what you will be experiencing while gaming.

In short, we are trying to measure the average color of all the pixels going from one frame to the next. No responsiveness test will be perfect, but anytime you take an average of many colors at once – grey is the best representation of that.

This is absolutely false. It’s true the human eye does have its own lag, and then there is the lag associated with reacting to what the eye sees (such as moving your thumb on a controller), but all of this takes place after the input lag described so far on this page. Factoring in this “human eye lag”, it would look something like this:

As you can see, the Input Lag of a display does matter. Any improvement in lag, whether it’s from the controller, the signal processing, the refresh rate, the computer itself, or even wearing the proper glasses – puts you at an advantage over someone who is on inferior equipment.

That being said, there is something to say about the lag times from human to human. Some of us are better at recognizing what is being displayed on a screen. Some of us are better at reacting to the change on a screen. This is why the pro player will win against a casual player 10 times out of 10 for a fast paced game – they have been practicing this talent, and may even have some sort of natural-born advantage (debatable). Either way, will shaving 10ms of lag off your game make you win every time? Probably not. But will shaving 10ms of lag off your game help you win more? Definitely.

This is the question with the most technical jargon to comprehend. Data in a cable (in the form of an electrical frequency) travels at about 1/100th the speed of light (source). So for any digital cable, we are talking about nanoseconds in lag, billionths of seconds. The lag is so small, and so insignificant, it makes no difference whatsoever to a professional gamer. When talking about other components of Input Lag, we are able to measure them in thousandths of seconds, so shaving off 10ms is a whole tenth of a second (it makes a difference). But cable speed is the most insignificant part of input lag by a large margin. What’s important to take away is that the monitor you purchase will always include a cable to support the highest refresh rate and resolution possible for that display. So this section shouldn’t matter too much, but for those interested here is the information anyway.

Adds support for 1080p at up to 240Hz (Y′CBCR with 4:2:0 subsampling), 1440p at up to 144Hz (Y′CBCR with 4:2:0 subsampling), and 4K at up to 75HZ (Y′CBCR with 4:2:0 subsampling), or 5K at 30Hz (Y′CBCR with 4:2:2 subsampling).

Adds support for 1440p at 240Hz (Y′CBCR with 4:2:0 subsampling), 4K at 75Hz (Y′CBCR with 4:2:2 subsampling), 4K at 120Hz (Y′CBCR with 4:2:2 subsampling), 5K at 60Hz (Y′CBCR with 4:2:0 subsampling), or 8K at 30Hz (Y′CBCR with 4:2:0 subsampling).

With chroma subsampling enabled, supports; 1440p at 240Hz (Y′CBCR with 4:2:2 subsampling), 4K at 120Hz (Y′CBCR with 4:2:2 subsampling), 5K at 60Hz (Y′CBCRwith 4:2:2 subsampling), or 8K at 30Hz (Y′CBCR with 4:2:2 subsampling).

With chroma subsampling enabled, supports; 4K at 144Hz (Y′CBCR with 4:2:2 subsampling), 4K at 240Hz (Y′CBCR with 4:2:0 subsampling), 5K at 120Hz (Y′CBCRwith 4:2:0 subsampling), or 8K at 60Hz (Y′CBCR with 4:2:0 subsampling).

1.4-1.4a: Natively supports the same specs that 1.3 natively supports. Adds optional support for DSC to allow: 4K at up to 240Hz, 5K at up to 120Hz, or 8k at 60Hz. With DSC and Y′CBCR with 4:2:2 subsampling enabled, it allows for 5K at 240Hz, and 8K at 120Hz. With DCS and Y′CBCR with 4:2:0 subsampling enabled, it allows for 8K at 144Hz.

origin of lag in lcd displays quotation

The mirror mode feature allows you to automatically left/right flip your image when your subject is viewing the display via a single mirror, without the requirement to manually adjust your stimuli.

We provide a 20m single link DVI fibre optic cable with each BOLDscreen 23 display. This is passed through the waveguide into the control room and connected to your host computer DVI output

origin of lag in lcd displays quotation

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