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Response Time, Input Lag, And Final Words

Acer, Dell, LG, And Samsung: Four 23" LCD Monitors, Rounded-Up
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In our first LCD round-up of the year, we put four monitors thorough our benchmark suite and find some surprising results. Even if you're an enthusiast with cash to spare, paying more doesn't guarantee a better display. Our tests explain why.

We first explored response times in our 22" LCD round-up, and the results here reflect what we've seen before. TN-based monitors continue to offer the best response times.

Those numbers don't reflect an aspect of real-world performance, though, so their utility is limited. That's why it's far more interesting to look at input lag.

Benchmarking lag with a camera is the fastest way to measure performance. Of course, normal cameras can't cut it, since they shoot at frame rates that are far, far too low for investigating split-second differences. Going the stopwatch route is no better as a result of human error. That's why we're using a 1000 FPS high-speed camera to measure the time between clicking the mouse and getting a muzzle flash in Call of Duty: Modern Warfare 2. Since one frame is equal to one millisecond, it’s possible to measure timing with a high degree of accuracy.

Benchmarking Absolute LCD Input Lag

Granted, there are issues with this approach. When you disable vertical sync in a game, the game engine renders at a rate different from that of the LCD. That doesn't change the refresh rate inherent to a monitor, though. Most LCDs, including the ones we're testing today, refresh at 60 Hz, which means that there can be up to a 34 ms variance between benchmark trials on the same screen. The problem is that there's no way to ensure that two LCDs are operating on the same refresh cycle. It's possible that the frame with a muzzle flash might get kicked over to the next refresh for one monitor, whereas it doesn't on another. That's why we take the average of five input lag measurements. 

This isn't a pure input lag test in the traditional sense. It's essentially the responsiveness you see in a gaming environment; it includes the time for the computer to process your movement. However, that idea of "total input lag" is what's really important, as it ultimately affects your reaction time. According to research published by Clemson University, the average college student has a reaction time of 200 milliseconds to visual stimuli. But, if you're a truly competitive gamer, you'll likely end up under 100 ms. What's your reaction time? Test yourself.

Compared to our previous 24” and 27" round-ups, it's not a surprise to see lower response times from the smaller 23" LCDs, since response time and input lag usually decreases with screen size. Why? Monitors with larger screens have higher pixel density, and as the number of pixels per inch (PPI) increases, so does the time it takes to refresh them all.

We sometimes find that the cheapest displays often have the lowest input lag values because there’s very little image processing occurring. As a result, they may instead sacrifice color gamut, luminance, and even uniformity. That pretty much reflects how the S231HL Bid achieves its input lag of 41 ms. In comparison, the IPS236V takes the longest of the models in our 23” round-up and still returns 57 ms.

Both extremes are still well below the 100 ms target that we specify for competitive games, though. If input lag is one of your primary concerns, the difference between these four displays is rather negligible.

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  • 10 Hide
    Flying-Q , February 22, 2012 7:27 AM
    I've noticed that Tom's seems to be focussing its attention on 23" 16:9 monitors. For the previous 3 years the most commonly advertised large monitors were 24" 16:9 with a noticable number of 24" 16:10 panels in the mix. I upgraded from a 19" 4:3 monitor 2 years ago to a 26" 16:10. At that time the market seemed to be flooded with 16:9 monitors.

    I have a friend with a 26" 16:9 monitor and he always wishes he had followed my choice for the vertical real estate gain. Going from 1080 pixels to 1200 pixels is just over 11% more space. That means MS Office can display two A4 pages side by side at life size even with the 'ribbon' showing.

    When gaming, the 1920x1200 resolution gives a greater feeling of being there due to the extra vertical space whilst maintaining the 'widescreen' ability to keep eye-attention.

    It seems that the computing world is beginning to be dictated to by the panel manufacturers who are geared for widescreen TVs in the same way that 4:3 computer moniters were originally just converted TV tubes. I have spent a lot of time in front of computer monitors over a great many years and I have found the 16:10 format to be the most satisfying to the eyes and the best for productivity.

    With these points in mind it seems that the computing industry is on the verge of losing a significant asset in the 16:10 format.

    Therefore,

    Toms Hardware will you please investigate the availability and future of this format.

    Q
Other Comments
  • 0 Hide
    compton , February 22, 2012 3:24 AM
    I thought the LG used not S-IPS but e-IPS, 6 bit + AFC. I actually thought it was almost identical to the CCFL backlit Dell U2311H (except the module is for LED backlight in the LG's case, not CCFL).

    I guess I was wrong.
  • 0 Hide
    compton , February 22, 2012 3:24 AM
    ^ I mean the panels, not the two monitors themselves.
  • 2 Hide
    klyzet , February 22, 2012 4:14 AM
    Im not sure if that input lag test is accurate.
    Why dont you guys test it the usual way? with a CRT monitor side by side running a timer (with ms ofc) and take some photos?
  • 0 Hide
    illusiongamer12 , February 22, 2012 4:26 AM
    why no review a viewsonic monitor they have a 150$-180$ monitor with these same specs
  • 4 Hide
    tlmck , February 22, 2012 5:34 AM
    Also noticeably absent is the ever popular ASUS brand. I don't have one myself, but it seems a lot of people do. Would have been an interesting comparison.
  • 2 Hide
    Eman25th , February 22, 2012 5:42 AM
    Can anyone tell me why the prices haven't dropped? i bought my asus 24" screen 2 years ago for 178$
  • 2 Hide
    acku , February 22, 2012 6:12 AM
    Quote:
    I thought the LG used not S-IPS but e-IPS, 6 bit + AFC. I actually thought it was almost identical to the CCFL backlit Dell U2311H (except the module is for LED backlight in the LG's case, not CCFL).

    I guess I was wrong.




    LG's QA website.
  • 2 Hide
    kyuuketsuki , February 22, 2012 6:12 AM
    I own the LG IPS236V, and I find your numbers completely non-believable. The contrast ratio is not that abysmal, and it can reproduce decent (though not the best, I admit) blacks. Also, on a review of the IPS226V, while being the 22" model, it is otherwise identical, and DigitalVersus found it to have a contrast ratio of over 1000:1. I'm wondering where the huge disparity in numbers is coming from, and I don't think it's DigitalVersus mussing things up.

    Question: did you go into the Menu > Picture and change the Black Level setting to Low? It defaults to High for some unknown reason, and at that setting the blacks are indeed terrible. At Low, the blacks are much, much better, and the slight decrease in white levels isn't much of an issue given that this is an extremely bright monitor.
  • 0 Hide
    kyuuketsuki , February 22, 2012 6:18 AM
    Also, what was the Gamma setting on the IPS236V?
  • 1 Hide
    acku , February 22, 2012 6:29 AM
    Quote:
    I own the LG IPS236V, and I find your numbers completely non-believable. The contrast ratio is not that abysmal, and it can reproduce decent (though not the best, I admit) blacks. Also, on a review of the IPS226V, while being the 22" model, it is otherwise identical, and DigitalVersus found it to have a contrast ratio of over 1000:1. I'm wondering where the huge disparity in numbers is coming from, and I don't think it's DigitalVersus mussing things up.

    Question: did you go into the Menu > Picture and change the Black Level setting to Low? It defaults to High for some unknown reason, and at that setting the blacks are indeed terrible. At Low, the blacks are much, much better, and the slight decrease in white levels isn't much of an issue given that this is an extremely bright monitor.


    Gamma set to 2.2. We did set to low. And as you know we measure luminance (nits) not illuminance (lux). Maybe this unit sat in the review pool too long... Not sure, but those were the readings that we achieved.
  • 2 Hide
    Anonymous , February 22, 2012 6:56 AM
    Please test also the absolute input lag of a CRT (you only have to do it once, I guess) for reference.
  • 10 Hide
    Flying-Q , February 22, 2012 7:27 AM
    I've noticed that Tom's seems to be focussing its attention on 23" 16:9 monitors. For the previous 3 years the most commonly advertised large monitors were 24" 16:9 with a noticable number of 24" 16:10 panels in the mix. I upgraded from a 19" 4:3 monitor 2 years ago to a 26" 16:10. At that time the market seemed to be flooded with 16:9 monitors.

    I have a friend with a 26" 16:9 monitor and he always wishes he had followed my choice for the vertical real estate gain. Going from 1080 pixels to 1200 pixels is just over 11% more space. That means MS Office can display two A4 pages side by side at life size even with the 'ribbon' showing.

    When gaming, the 1920x1200 resolution gives a greater feeling of being there due to the extra vertical space whilst maintaining the 'widescreen' ability to keep eye-attention.

    It seems that the computing world is beginning to be dictated to by the panel manufacturers who are geared for widescreen TVs in the same way that 4:3 computer moniters were originally just converted TV tubes. I have spent a lot of time in front of computer monitors over a great many years and I have found the 16:10 format to be the most satisfying to the eyes and the best for productivity.

    With these points in mind it seems that the computing industry is on the verge of losing a significant asset in the 16:10 format.

    Therefore,

    Toms Hardware will you please investigate the availability and future of this format.

    Q
  • 7 Hide
    amigafan , February 22, 2012 7:56 AM
    Tom's hardware readers are mostly developers who need 16:10 (extra vertical space) not 16:9 (for movies). I would like to see 16:10 monitors reviewed.
  • 5 Hide
    dww , February 22, 2012 8:37 AM
    I'd like to add to the call for reviewing 16:10 monitors.

    I love my 1920x1200 Samsung 2443BW but worry that when it needs replacing there won't be any affordable replacements. Tom's can't tell manufacturers what to do but perhaps more reviews would result in more sales and hence more interest in making 16:10 displays.
  • 2 Hide
    __-_-_-__ , February 22, 2012 9:24 AM
    Eman25thCan anyone tell me why the prices haven't dropped? i bought my asus 24" screen 2 years ago for 178$

    it reached the lowest price point. you can't expect to buy an LCD for 1$.
    remember CRT TV's. they were produced for over 50 years, yet the price remained the same for several years after reaching a certain minimum.
    It will be the same with OLED and AMOLED. currently you can buy a 17" OLED for 4k$. in some years in the future you can buy a 24" OLED for 178$. Just like you did for your LCD.
  • -5 Hide
    Anonymous , February 22, 2012 11:03 AM
    I suspect the truth is - a display is a display is a display. For all but the very specialised applications
    around - they are probably all more than good enough. I'd rather someone warned me that my
    black samsung bled light round the edges - had a dark "reflected shaddow" along the top edge of the image about 4mm down if it was slightly higher than my eyeline (caused by the shiny black plastic case - not as I originally thought - by dead LCD electronics - its a weird effect)

    I'd like reviewers to get out of the tech details and into the real world.

    Another example of this is video cards. I neither know nor card how they work. For all intents
    and purposes the only reason to have a better graphics card is to play games. Very little else
    has any reason these days.

    And I dont want to know how many pixels a second in mode 2 with X operaing system and Z memory
    it can do.

    I want to know where the new card sits IN RELATION to my existing card for ease of play.
    Nothing else anyone says helps me choose. And no one seems to do that.

    I read the review here this week to see if upgrading my GT320 card would play Far Cry better.
    I still havn't the faintest idea. Not a clue. I'm getting the sense that others are reluctant to upgrade
    just to get the newest thing on the block these days too. Just because its newer and even performs better doesnt mean its worth having.

    And guess what. I design electronics for a living so I'm not dumb to tech talk. So whats the point?
    Lets have reviews targeted at users not specification matching.



  • 1 Hide
    spookyman , February 22, 2012 11:51 AM
    lol...

    Why not buy ASUS 24" LED monitor over these? The picture quality is better and you can get it less then $200 sometimes on New Egg.
  • 1 Hide
    Marcus52 , February 22, 2012 12:11 PM
    There have been some new 1920x1200 monitors released in the last 6 months, so the format is far from dead.

    ;) 
  • 0 Hide
    jgutz2006 , February 22, 2012 1:29 PM
    Why arent more monitors shipping with DisplayPort? need more non legacy displays out there for Eyefinity/Nvidia Surround!
  • 4 Hide
    warezme , February 22, 2012 1:42 PM
    I'm tired of cheap (as in quality) 1920x1080 monitors. The industry is stuck on making a cheap product for a quick buck.
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