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Response Time, Input Lag, And Final Words

Three 27" IPS LCDs: UltraSharp U2711, DS-277W, And MultiSync PA271W
By
Brand
Panel
Response Time
Full Black-to-White
Dell SR2220LTN
16 ms
LG E2241VTN
17 ms
Samsung S22A350HTN
18 ms
Acer GD235HZ
TN
16 ms
Dell U2711
H-IPS
23 ms
DoubleSight
H-IPS
21 ms
NEC PA271W
H-IPS
20 ms


We explored response time measurements in our 22" LCD roundup, but those monitors were all TN-based. IPS is a completely different technology. Moreover, today's Larger monitors employ a more evolved form of the technology called H-IPS, which improves contrast ratios and allows for more natural white production. Despite the fact that they're newer than what we saw five year ago, their response times are still typically slower than what we see from TN-based LCDs.

How Fast Can You Frag?How Fast Can You Frag?

Benchmarking that lag with a camera is the fastest way to measure performance. Of course, normal cameras won't cut it, since they only shoot at 29 FPS. That's unacceptable if you're trying to measure precise time differences. Going the stop-watch route is no better due to human-introduced errors. 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, you're letting the game engine render at a rate different than that of the LCD. However, that doesn't change the refresh rate inherent to a monitor. 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 monitor. 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 screen refresh for one monitor, whereas it wasn't there on another. That's why we took the average of five input lag measurements.

Brand
Panel
Response Time
Full Black-to-White
Total Input Lag
Acer GD235HZ
TN
16 ms
73 ms
Dell U2711
H-IPS
23 ms
98 ms
DoubleSight DS-277W
H-IPS
21 ms
82 ms
NEC PA271W
H-IPS
20 ms
115 ms


Arguably, this isn't a pure input lag test. It's more akin to the responsiveness you'd see while gaming, because 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.

Which three are H-IPS? Can You Take A Guess?Which three are H-IPS? Can You Take A Guess?

If you possess superior gaming abilities, there are some differences  between these three models. NEC's PA271W has a slightly more lag due to hardware circuity that's preprocessing color information. Interestingly, DoubleSight's DS-277W does relatively well. Meanwhile, Dell's U2711 operates in the middle of the road, just under 100 ms. The broader point here is that, fortunately, input lag is becoming less of an issue on the latest IPS-based LCDs. If you don't fall into that group of gamers, there's very little to worry about. Clearly, today's H-IPS panels offer better performance than yesterday's S-IPS based LCDs.

What monitors do you want to see us review next? Tell us below in the comments section! A special thanks goes to Accell Cables who sent over an UltraAV DisplayPort to DVI Dual-Link Active Adapter to assist in testing.

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  • -2 Hide
    terr281 , August 11, 2011 5:17 AM
    What monitors to review next?... As many people said in the review of the 22" TN panels from your last review, the next review should include "enthusiast available" ~23" panels. (Instead of just big box "Buy from Best Buy" models.)

    The lowest price of the three 22" TN panel monitors you reviewed was $180. A quick Newegg search shows several similar panels from names such as Acer, Asus, etc. starting at $140. (And, in the gaming, as well as office environments, 2 or 3 monitors are now more common than one single large one.)
  • 1 Hide
    nevertell , August 11, 2011 5:27 AM
    IPS vs VA in gaming.

    Although just a regular sum up of the available 22-24 VA panels would be great.
  • 2 Hide
    Anonymous , August 11, 2011 5:49 AM
    Thank you for the excellent and thorough review. Perhaps next time, the new Apple 27" Thunderbolt display can be thrown into the mix. For a lot of video and photography pros like myself, the Apple display is considered to be the "standard" and I would love to see how it stacks up again the competition. Also maybe throw in a professional level Eizo display as well to show the difference between a ~$1000 display and a $3000 display.
  • 4 Hide
    Anonymous , August 11, 2011 5:57 AM
    The new Apple Thunderbolt 27" display - would be nice to see if it's worth the money
  • 8 Hide
    Anonymous , August 11, 2011 6:03 AM
    120hz monitors lead the way

    You should review a 2560x1600 120hz IPS monitor.

    Oh wait...
    2560x1600 isn't supported at 120hz over DVI-D (dual link)
    IPS monitors can't do 120hz with today's technology

    Bummer!

    :( 

    F
  • 5 Hide
    agnickolov , August 11, 2011 6:16 AM
    I'd recommend the same IPS review applied on affordable 24-26" monitors that most of us would actually potentially buy. It's nice to dream about 27"+ 2560x1440, but let's get back to reality with 24" 1920x1080 and 1920x1200 (if still available) IPS monitors please. (At least until higher resolutions enter mainstream price points.)
  • 0 Hide
    crisan_tiberiu , August 11, 2011 7:04 AM
    I have a 22" Philips LED Backlight monitor and i am very happy with it . I dont see any Philips monitors in any of your reviews, why is that? :) 
  • 0 Hide
    boletus , August 11, 2011 7:25 AM
    Nice roundup, it had me measuring what a 26" wide monitor would look like on my desk. However, you need to fix the title block in the table for the NEC monitor on the "Black And White Uniformity" page (it says Samsung S22A350H).
  • 0 Hide
    soccerdocks , August 11, 2011 7:38 AM
    On the "Black And White Uniformity, Viewing Angles" page the 3rd table states that it is for the Samsung S22A350H when it is actually for the NEC.
  • 1 Hide
    Anonymous , August 11, 2011 8:29 AM
    Thank you for this comparison, very interesting reading!

    I am somewhat disappointed that 27" monitors nowadays don't use 2560*1600 panels.
    That resolution makes much more sense to me for a monitor that is not targetted at the average consumer.
    Personally I would love a 2560*1920 (or 2048) screen @ 120Hz, but if I understand correctly link speed becomes an issue here.

    Why is it that displays for mobile phones are increasing in pixel density, but desktop displays don't improve in this regard?

    For a next review I would really like to get a better understanding of (high-resolution) 120Hz monitors. What are the (dis)advantages of 120Hz for regular/2D usage, etc...
  • 0 Hide
    Jax69 , August 11, 2011 8:59 AM
    wait for Samsung's PLS and other iterations of the panel from different brands.
  • -3 Hide
    pirateboy , August 11, 2011 9:47 AM
    please review Asus PA246Q and any other 24 inch 16:10 screens you can get your hands on...please don't review anymore 16:9 screens
  • 0 Hide
    bavman , August 11, 2011 12:40 PM
    I wish i could afford one of these beautiful monitors =(
  • 0 Hide
    jacobdrj , August 11, 2011 1:14 PM
    30" Dell IPS, Apple Cinima Display, IMac 27/30" display, TV's for use as TV monitors. 3d Monitors. Quad LCD monitors (RGB+Yellow)... Projectors, including lag time...

    CNet used to do stuff like this, so did PC Mag. They stopped. Bothers me. I have to rely totally on Amazon/Newegg/TigerDirect user reviews for screen info.
  • 1 Hide
    Soul_keeper , August 11, 2011 1:44 PM
    "But then there are the folks who simply prefer a single workspace and ultra-high resolutions."
    ^^ me
  • 1 Hide
    lbwmoo , August 11, 2011 2:33 PM
    I too would like a better explanation on the issue of pixel density. In 2002 you could order a laptop from dell with a 15" UXGA screen with 1600x1200 resolution. It was a gorgeous screen then, and doesn't look bad now. Standalone desktop monitors, however, with that resolution start at 20" minimum. You can get 1920x1080 at screen sizes starting around 21.5" and ranging to 27" that I've seen in stores. Are there benefits to packing the same resolution into the smaller package, such as smaller pixels leading to crisper image? Is there a "sweet spot" to this resolution that balances pixel size and density vs overall space?

    It seems that 1920x1080 is the new norm, which is annoying because I don't see why I should have to give up vertical resolution just to fit the standard of the current high definition videos. 16x9 vs. 16x10 is a debate right now for me. I would rather have 16x10 because more screen real estate is better, but it seems that the 16x10 front has stagnated. All the new goodies are going into 16x9, with the exception of the 30" 2560x1600 models.
  • 0 Hide
    pirateboy , August 11, 2011 3:21 PM
    jacobdrj30" Dell IPS, Apple Cinima Display, IMac 27/30" display, TV's for use as TV monitors. 3d Monitors. Quad LCD monitors (RGB+Yellow)... Projectors, including lag time...CNet used to do stuff like this, so did PC Mag. They stopped. Bothers me. I have to rely totally on Amazon/Newegg/TigerDirect user reviews for screen info.


    here is an excellent screen review site
    http://www.prad.de/en/monitore/index2.html
  • -1 Hide
    ram1009 , August 11, 2011 3:38 PM
    These hi res monitors are just another case of diminishing returns. You spend several times the dollars as you would on equivilent standard res monitors for a fractional improvement in performance. These are definitely not main stream items. The last time I looked Newegg only offered one monitor in this res range.
  • 1 Hide
    tmax , August 11, 2011 4:26 PM
    Nice monitors but way too much money.
  • 0 Hide
    compton , August 11, 2011 5:35 PM
    Thanks for your excellent review, Andrew. I'd like to see a 24" roundup of IPS/e-IPS. Dell has their new 2412 16:10 24" e-IPS paneled Ultrasharp out, but it's not high gamut like the 2410 and especially the 2408 (which is S-PVA, fantastic, and not for everyone). e-IPS is marching on to higher adoption, and it would be great to see how these e-IPS displays stack up.
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