Display Lag and Response Times

We've heard frequent complaints about "input lag" on various LCDs, so that's one area we look at in our LCD reviews. You might be wondering why we put input lag in quotation marks, and the reason is simple: 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 simple "display lag".

To test, we run the Wings of Fury benchmark in 3DMark03, with the resolution set to the native LCD resolution -- in this case 1920x1080. 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.) Again, we know some of you would like us to compare performance to a CRT, but 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. 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.

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.

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. Here is a summary of our results. Images for the E2200HD and E2400HD can be found on pages four and seven of this review; images for the remaining LCDs are available in our 24" LCD roundup.

Display Input / Processing Lag vs. HP LP3065
  A B C D E F G H I J Avg. (ms)
ASUS MK241H 10 0 0 0 0 0 0 0 0 0 1
BenQ E2200HD 0 0 0 10 0 0 0 0 0 0 1
BenQ E2400HD 0 0 0 10 -10 0 -10 0 0 10 0
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

Processing Lag Comparison

As mentioned previously, all of the S-PVA panels we have tested to date show a significant amount of input lag, ranging from 20ms up to 40ms. We will have a look at an MVA panel in the near future, which will hopefully show results similar to the TN and S-IPS panels, but for now we can only recommend avoiding S-PVA panels if you're concerned with input lag.

BenQ E2400HD Evaluation Brightness, Contrast, Gamut, and Power
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  • shithead3656 - Tuesday, March 31, 2009 - link

    Very nice revie. I only read the e2200hd review bcoz i plan to buy that model once my 17" CRT goes BOOOOM. xD

    Anyways, I wish you guys can review the Samsung 2233SW(which is benq's E2200's rival)(Guys, i know the samsung has no speakers and HDMI, but usually monitor speaker ain't good and you can buy HDMI>DVI converter). But im my contrie, Samsung 2233SW is steadily going up in price, so bcoz of that I'm also looking at Samsung 2033SW. I will be waiting. And you guys at anandtech ROCK!
    Reply
  • swordenium - Friday, May 1, 2009 - link

    Go for the 2233SW!! or preferably Its older bro 2243SWX which has more features and includes a DVI cable!!! Both Asus Vh226H and Benq E2200HD are gr8 monitors for price yet Image quality and colors(too unnatural Benq) leaves a lot to be desired!!!! so so......but Samsung 2233SW (reviewed by techtree and pcworld)and 2243SWX are accurate in colors!!! and have awesome IQ!!! Just it lacks HDMI input! which I dont care!! DVIs handle HD resolutions well!! of course, u have a hdmi to dvi converter!! Reply
  • tofool - Monday, February 23, 2009 - link

    how do you remove the base stand as pictured in the article? Reply
  • Jalamari - Monday, February 23, 2009 - link

    hi i had some trouble with the base stand too but got it finaly.

    the screws holding stand are behind the small silver plastic piece where the monitors tilts, it has 4 clips on top and bottom so you should be able to remove it by squeezing the plastic from top and bottom and pulling it away from monitor if its too tight try to help it with flat screwdriver


    Reply
  • virtuoso5 - Monday, December 1, 2008 - link

    Is it true that this display does not work good with 720p signals?
    I wanted to buy this to connect also the Playstation 3 and most games are 720p (the console makes no upscaling to 1080).
    Reply
  • zzzxtreme - Monday, December 1, 2008 - link

    I just tested connecting my laptop to a 32" Samsung 720p LCD TV through VGA. LCD TV's brightness are typically from 450nits-500nits.
    It is freaking beautiful. You get all the quality panels and chipsets.
    The days of monitors are over.
    Reply
  • Benyss - Sunday, November 30, 2008 - link

    Please HELP. Benq 2400HD ror PS3? Yes or No? Thanks. Reply
  • Tonyjr - Wednesday, November 19, 2008 - link

    They further dropped the price of E2200HD for "early black friday" $209 promo code "E2200HD".
    Reply
  • Cashmoney995 - Monday, November 10, 2008 - link

    The best thing that I have going on in my APT is my cheap 12$ VGA clone box I got from monoprice. I currently have my 16:10 1680x1050 display cloned to my Samsung 50 inch LED DLP tv in my living room. Added in a wireless kb and mouse and I can access the same computer in my office in my living room. Ahh the beauty. EXCEPT that 1680x1050 has some weird cut offs on the DLP. With a real 1080P monitor I can clone my desktop perfectly on the tv. Reply
  • nubie - Wednesday, November 5, 2008 - link

    I am looking for a real 1080p display for about this price as a TV, but the lack of 1080i or 720p support is kind of a deal killer.

    I am just assuming 1080i isn't supported, but what do I know?

    If you have a tuner/DVD player that will support 1080p output then I would love to use this screen. Pixel splitting is a pet peeve of mine and I love the crispness of a 1:1 source and display ratio.
    Reply

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