Input Lag and Response Times

We've heard frequent complaints about input lag on various LCDs, particularly after our last review of the Samsung 245T. We decided it was time to take a closer look at the subject and see if we could come up with a repeatable test. We ended up settling on a test similar to what we were using to show response times, with a few changes.

We run the Wings of Fury benchmark in 3DMark03, with the resolution set to the native LCDs resolution -- in this case 1920x1200. Our test system is an overclocked quad-core Q6600 (3.30 GHz) running two Radeon HD 3870 cards in CrossFire on a Gigabyte GA-X38-DQ6 motherboard. (This is the same system used in our initial testing of 3DMark vantage.) 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 input lag. (The lack of a built-in scaler probably has something to do with this.) [Ed: Before you ask, no, I do not have any CRTs around that I can use as a reference monitor, and frankly I don't want any. They're huge, heavy, and require more power, and the best ones were made over five years ago. Sorry - LCDs are where everything is heading. R.I.P. CRT.]

While the benchmark is looping, we snap a bunch of pictures of the two LCDs sitting side-by-side. We set our camera to f/2.2, ISO-400, and a 1/400 sec exposure in order to get a clear snapshot of the on screen action. (Note that these settings have changed from previous articles.) 3DMark03 lists a runtime with a resolution of 10 ms at the bottom of the display, and we can use this to estimate whether a particular LCD has more or less input lag in our reference LCD. We then 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 input lag value.

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 any measurement less than approximately 17 ms is not 100% accurate. Second, the two LCDs can have mismatched vertical synchronization, so it's entirely possible to end up with a one frame difference on the time readout purely 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 input lag/internal processing delay.

Here is a summary of our results, followed by a sample image chosen to highlight the pixel response time of the LCDs. Despite what the manufacturers might advertise as their average response time, we found most of the LCDs were equal in this area -- they all show roughly a one frame "lag", which equates to a response time of around 16 ms.

Display Input/Processing Lag vs. HP LP3065
  One Two Three Four Five Six Seven Eight Nine Ten Average (ms)
ASUS MK241H 10 0 0 0 0 0 0 0 0 0 1
Dell 2407WFP 10 20 30 20 10 10 30 30 10 20 19
Dell 2408WFP 30 40 40 40 30 30 40 30 50 50 38
Gateway FHD2400 -10 -10 0 10 10 10 0 10 10 0 3
Gateway FPD2485W 30 10 20 20 20 10 0 30 20 20 18
HP w2408 10 10 0 0 0 0 0 10 0 0 3
LaCie 324 40 30 40 30 40 50 40 50 50 30 40
Samsung 245T 30 30 30 30 30 20 30 30 20 20 27
Samsung 2493HM 0 10 0 0 0 10 0 -10 0 10 2


ASUS MK241H


Dell 2407WFP


Dell 2408WFP


Gateway FHD2400


Gateway FPD2485W


HP w2408


LaCie 324


Samsung 245T


Samsung 2493HM

The table tells a clear story: all of the S-PVA panels as we mentioned clearly have more input lag/internal processing lag than all of the TN panels. This is a pretty shocking result, as it indicates that the problem may actually be inherent in S-PVA technology, although there are still panels that do better in this area. The Gateway FPD2485W and Dell 2407WFP both have an input lag just under 20 ms -- or a one frame delay on average. The Samsung 245T has a 27 ms delay on average, indicating it would be one or two frames behind what is actually happening. Worst of all are the Dell 2408WFP in the LaCie 324, which have a two or three frame lag. (This is discounting any other lag that is present between the user and what they are seeing on the display; there's also a slight amount of lag associated with reading input from your mouse/keyboard, processing that input, rendering the resulting image, and sending that to your display.) In contrast, the four 24" TN panel LCDs all more or less match the HP LP3065.

Thus, we have no choice but to conclude that if you are seriously concerned about input lag, you will have to sacrifice viewing angles, color accuracy, and/or overall display quality in order to avoid this on the current 24" offerings. On the other hand, we have played games on all of the test LCDs, and we honestly can't say that we noticed any difference in our overall performance. But we weren't hopped up on Bawls and we don't have a 1337 name like Fatal1ty. Competitive gamers will probably feel differently.

Samsung 2493HM Evaluation Brightness, Contrast, Gamut, and Power
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  • Bolas - Friday, July 31, 2009 - link

    Anand,

    Any chance of a 30" monitor roundup for those of us wanting to buy an extreme HD monitor to go along with the new high end gaming computer we're buying around Christmas time?

    I'm not sure which is best between the stuff currently on the market (or things coming out in the near future, say by Christmas). I've heard of:

    Dell 3007WFP
    Dell 3008WFP
    HP LP3065
    Gateway XHD3000
    Samsung Synchmaster 305T
    Apple Cinema 30"

    Am I missing any 30" monitors currently available? Which is the best, regardless of price? Which is the best in terms of bang-for-the-buck? Which is "future-proof", with good connectivity? I plan to use it to play Starcraft II and Warcraft III and maybe some Everqeust.

    I just turned 40, so as part of my mid-life crisis, I'm buying a high end gaming computer, probably a CyberPower Black Mamba or a Digital Storm of some kind, depending on how the stock market does.

    Basically an overclocked Core i7 with three-way or quad SLI. My computer budget is $4000 to $6000, not including monitor price, and I can get a nicely configured Cyberpower for about $5400 last I checked. But what to use to display all that computer goodness? I figure to spend $1000 to $2000 on a 30" monitor, but which one?!?

    Thanks!
    -Bolas
    Reply
  • szore - Tuesday, June 23, 2009 - link

    I bought this for about $269 free tax and shipping and I love it for gaming. Reply
  • jpp - Monday, September 15, 2008 - link

    Hi,

    First of all a big thank you for these reviews - they are top notch.

    I'm currently trying to decise between the Samsung and the Dell. I'm not into gaming, so latency doesn't bother me. Nor for that matter do the plethora of inputs both provide - I'll just be using with the one DVI input at native resolution.

    Living in PAL country, I would be delighted if either of these monitors do 50Hz FR. I doubt it very much, but thought it worth asking. I know that my large Samsung 405T wasn't specified at 50Hz, but it is able to do it natively nevertheless which makes for judder free PAL DVD and FTA TV program watching on the screen.

    So, apart from this probably undefined/untested aspect, which would be the better choice, given as I say that I am not interested in gaming?

    I bring this comparison up here as this review does not list the Samsung in its comparison table. The Dell was the editor's choice, but the Samsung was reviewed after this 24in line up, so I was wondering if it could be included somewhere in the ranking?

    Thansk again for the tremendous effort that goes into the testing and reporting.

    Phil.

    Reply
  • jpp - Monday, September 15, 2008 - link

    As I can't edit my previous post, just a correction wrt the timing of the 2 reviews.

    The Samsung review was done before the 24in panel review, yet it's not listed in this review. That seems a bit odd and I was wondering why that is the case?
    Reply
  • billingsgate - Monday, May 26, 2008 - link

    I can't find reviews anywhere of Eizo LCD monitors. Eizo has a great reputation, but that's all I seem to be able to go on. A salesman gave me a really good pitch for the Eizo FlexScan S2401W. It's a Samsung TN panel (he claims), but somehow being an Eizo it's much better for color quality than any Samsung in the price range. It seems to be a good candidate for balancing accurate color and minimum input lag. But I can't be sure, since I can't test it in the shop for any of those things, plus the shops where I live are all little cubby holes in computer centers, with minimum choice in each shop, so it's impossible to do any side-by-side comparisons between Eizo, Samsung, NEC, etc., since they're never together in the same place.

    Any thoughts on Eizo's (relatively) budget line of FlexScans?
    Reply
  • silvajp - Sunday, May 25, 2008 - link

    Today I bought a Samsung 2693HM for $600 - $50 rebate and I am blown away. It looks great - very bright and vibrant. I am wondering if it has the same low input lag as the 2493HM. The resolution is 1920x1200 so at 25.5" it's got bigger pixels which is just fine for my poor tired eyes.

    Reply
  • billingsgate - Thursday, May 15, 2008 - link

    Can someone help me with a recommendation? After reading billions of reviews of monitors I am confused as hell? is there a "best compromise" LCD monitor for both color accuracy and least lag time?

    I am not a gamer. I am an animation professional, and I heavily use Wacom tablets for drawing, loose and freehand, with Photoshop, Flash, and various professional animation programs. I've always used a CRT monitor and never once have experienced any lag between my stylus movement and lines on screen. I do own a Compaq tablet PC, and when I draw on-screen, the lag is perceptible enough to make the drawing very unnatural and inhibited. I just can't draw freehand that way.

    As my beloved, expensive flat screen Samsung CRT monitor is now dying after 7 years of heavy use, I'm in the market for an LCD. In my business I need both excellent color accuracy and zero or minimal lag time for stylus input. Where I live (Hong Kong) there isn't a single shop that would ever allow me to test such a setup, so it's a lottery for me. Plus, their in-store demonstrations for color "accuracy" are geared for Asian tastes, which is heavy HEAVY on oversaturated red (while westerners prefer oversaturated green).

    After poring through all the reviews, particularly on this site, I can't even narrow down the choices to 4 or 5 candidates. The Dell 2408 looks amazing except for lag time. The Samsung XL20 (not widescreen, but I don't really care) looks great for color and no lag time, but it has a noisy fan (irritating!) and is a bit smaller than I want.

    Can someone seriously help me to narrow the potential choices for something that has good or great color and minimal input lag? I won't ever use it for gaming or for TV or video viewing.
    Reply
  • hjkelly - Thursday, May 15, 2008 - link

    I'm in a similar spot - into editing photos and watching movies. I was almost set on the Dell 2408, but then I found out it has about four frames of lag, which wouldn't be fun for movies (or drawing with a Wacom tablet, I'm sure). I've finally settled on DoubleSight's DS-263N. If you want a quick summary, it's like an Apple Cinema display, but 26" and with a polarizer to get rid of the white haze at wider angles. It's also very fast, less than one frame's delay, I believe. It's around $700, but the catch is that it's hard to find in stock, so you'll have to be on your toes to get one. But isn't that just a sign of quality, really? =) Reply
  • JarredWalton - Friday, May 16, 2008 - link

    Surely you know someone over there that can let you borrow an LCD to test out? Honestly, I don't think you'll experience problems with input lag - we're talking about 50ms or so relative to a CRT, so 1/20 of a second. What you've noticed on a tablet PC probably has a lot more to do with the lack of processing power and other differences. All you really need to do is find someone with an S-PVA 24" LCD and you can see if you notice lag. I can game fine on the 2408WFP - the lag is just barely perceptible at times, but not enough to cause me problems. But I'm not a competitive gamer.

    As for DoubleSight, their 26" LCD is about to be phased out apparently - I asked them for a review sample and they said it was at EOL. It may become even more difficult to find in stock shortly.

    Anyway, I hear good things about a few MVA panels (that I haven't ever seen let alone tested), or if money isn't a serious concern just pick up something like the HP LP3065. For professional use, I have a hard time finding anything I would prefer to a nice S-IPS 30" LCD. And the 2560x1600 gaming resolution is nice as well.
    Reply
  • billingsgate - Friday, May 16, 2008 - link

    Actually, I don't know anyone with an LCD screen to borrow, other than my son's cheap one which is fine for gaming but not even close to being color accurate, so not exactly a good example. I can tell you that I tried a Wacom Cintiq tablet, which is essentially an LCD screen you can draw on. It was connected to a G5 Mac, so no lack of processing power. The lag on that was a fraction of a fraction of a second. But I kept finding my hand slowing down to let the line catch up to the stylus, which sucked all the spontaneity out of my drawing. In other words, for a "sensitive artist", even a small lag is noticeable. With the Cintiq I attribute it to the signal having to travel round trip on a USB connection. But I am now quite concerned about buying the wrong LCD and being stuck with it. This isn't the USA. Once you buy something and leave the shop, there is no such thing as returning it.

    So, to repeat my question: can you or someone help to recommend a shortlist of monitors that are both good to great for color accuracy, and minimal for input lag?
    Reply

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