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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  • 10e - Wednesday, November 5, 2008 - link

    If the last MVA panel from BenQ/AUO is any indicator, input lag should be low. I had the FP241VW with December 2007 firmware and it was 7.9ms behind a CRT, with only 5% of the time it being 2 frames behind. The other times it was only 1 frame behind, or none at all.

    It's good to see that our crying over on another forum has kept BenQ and AUO from abandoning the non-TN market altogether

    The only tiny issue with it was dark greys shifted more than (say) my Dell 2709W (S-PVA). Good luck with the review.
  • Jorgerr - Tuesday, November 4, 2008 - link

    Did you check the Samsung T220P? looks that have the same specs as the Benq. Seems to be a very interesting competitor as well.
    I would appreciate to read your comments about it.
  • JarredWalton - Tuesday, November 4, 2008 - link

    Looks like that was an Asian release only? I'm not sure... spec-wise, it's actually a 1920x1200 LCD, and I haven't seen any of those in 22" trim over here in the US. Weird. Honestly, I wouldn't be surprised if Samsung makes the panel in the BenQ LCDs; then again, it's either Samsung, AU Optronics, or Chi-Mei so I have a 33% chance of guessing right. ;-)
  • Jorgerr - Tuesday, November 4, 2008 - link

    Thanks :-) In Israel the Samsung T220P is available, and we belongs to Asia.
    Good luck with the new president! No matter who will be I wish you the best.
  • NARC4457 - Tuesday, November 4, 2008 - link

    [quote]We are only aware of one other 22" LCD manufacturer that offers native 1080P support (ViewSonic), and we feel this is an untapped market.[/quote]

    Check out Dell's new 2209W, it is a Full HD 22" LCD
    http://accessories.us.dell.com/sna/products/Displa...">http://accessories.us.dell.com/sna/prod...mp;dgc=C...
  • JarredWalton - Tuesday, November 4, 2008 - link

    I edited the conclusion for you - I should have known better than to make an assumption without a bit more research. Probably HP has a similar display too - or it's in the works. Obviously, where one LCD company goes plenty will follow, and if there aren't more 22" 1080P LCDs right now I expect that to change. The Dell 2209W appears to lack HDMI input, however, so that's a big advantage for the BenQ and ViewSonic options IMO.
  • NARC4457 - Wednesday, November 5, 2008 - link

    True enough, I was surprised that they didn't have the same amount of inputs that many of their existing monitors already have.

    Wasn't looking for an update to the article, just wanted to send it your way in case you were looking for more monitors to review. :) Thanks jared, good information in the review.
  • strikeback03 - Wednesday, November 5, 2008 - link

    Probably all use the same LCD panel - once the panel becomes available, the usual suspects will all build a display around it.
  • Flyboy27 - Tuesday, November 4, 2008 - link

    I know I want to step up to 1920x1200 or 1920x1080 so that means a 24" monitor. They seem to be the sweet spot right now as you can get a video card these days to run those resolutions in almost every game for a very reasonable price. However, there's no reason for me to upgrade my HD3850 until I get a bigger monitor since it runs all games just fine at 1440x900. I'm sure there are many other folks out there that are in the same boat.

    Now, it's easy to figure out comparatively which video card to get by reading Anandtech and other such sites but harder to find info on 24" monitors. Not too hard to compare FPS in a certain resolution and find a video card to get the best bang for your buck. However, for a guy that is a gamer, movie watcher, internet browser, and avid Photoshop user what monitor is the best bang for the buck. I don't want to sacrifice panel speed for colors. My idea with colors and Photoshop is just get me "close enough" and I'll be happy. I'm also on a budget (that's why I'm not looking at 30" monitors). Where is the happy medium here guys? -Thanks
  • JarredWalton - Tuesday, November 4, 2008 - link

    I have a BenQ MVA panel up next for review, along with a couple other 24" LCDs. I'm going to be very interested to see if the MVA panel can offer colors and viewing angles equal to S-PVA but with processing lag equal to S-IPS/TN. Stay tuned....

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