Response Times
A topic that usually comes up as a problem with LCDs is their slower response times relative to CRTs. While there's no doubt that even the best LCDs still exhibit some slight pixel smearing, the vast majority of users are okay with the level of performance we have available now. We also find it extremely difficult to tell the difference between various LCDs with response times ranging from as low as 2ms all the way up to 16ms. As with other specifications, there appears to be marketing influence on the final reported numbers.
To try to illustrate response times, we use our camera set to 1/80s shutter speed and a 2.5 F-stop at ISO-400. However, taking a picture of a display using a high shutter speed still isn't the same as looking at the display in person. LCDs run at a refresh rate of 60 Hz, and we use a shutter speed of 1/80s, so the net result is that we will capture an image of the display as it appears over a short period as opposed to an instantaneous look at the state of the various pixels. Image retention on your retinas also occurs, so even if you can eliminate the smearing effect at the display level you won't necessarily "see" a perfectly crisp transition. Then you have to consider some of the latest games are adding motion blur back in using DirectX 9/10 in order to make things look more realistic... but in that case, it's an artistic effect rather than a technological defect, right?
Links to previous response time images are below, taken during the Game 1 demo in 3DMark03.
Acer AL2216W #1 Acer AL2216W #2
Dell 2405FPW #1 Dell 2405FPW #2
Dell 2707WFP #1 Dell 2707WFP #2
Dell 3007WFP #1 Dell 3007WFP #2
Gateway FPD2485W
HP LP3065 #1 HP LP3065 #2
HP w2207
HP w2408
 MPA Off |
 MPA On |
Samsung advertises a 5 ms gray-to-gray (GTG) response time, although it's not entirely clear whether that figure is with MPA enabled or disabled. We tested response times and configurations, and we would be hard-pressed to tell the difference. In our best-case images, the 245T does appear to have slightly better response times than other 24" LCDs that we've reviewed, but the actual difference is probably less than a couple milliseconds. We're not sure about the rest of you, but our eyes just aren't sensitive enough to tell the difference between 6/1000s and 8/1000s, even if the first is theoretically 33% less time.
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AnnonymousCoward - Monday, February 11, 2008 - link
Jarred, Jarred, Jarred...IMHO, this monitor is total garbage and unusable due to input lag. I don't think you should shrug it off since you can't detect it, as it is a big issue for many people.
Check out this great chart: http://www.tftcentral.co.uk/images/samsung_xl20/in...">http://www.tftcentral.co.uk/images/samsung_xl20/in...
You talked about measuring input lag...well, it's true that 2 DVI output ports could have a lag between the two, but we notice that they don't since the chart shows lags ranging from 1.6ms to 58.8ms (taken from average readings). That data validates user experiences, as well. Other sources have found that the 244T/245T have 55-65ms of input lag, and that the ports don't matter: http://tinyurl.com/2xl857">http://tinyurl.com/2xl857
Even if you can't perceive that, think about it in terms of ping. Is a 60ms ping the same as 120ms? This monitor effectively adds 60ms to your ping! And regardless of games, this isn't at all acceptable to me for a mouse cursor in Windows; the delayed feedback makes it harder to precisely point at anything.
Thanks anyway for the review, and normally I enjoy your writings.
JarredWalton - Monday, February 11, 2008 - link
Here's the problem with that chart of input lag:The GPU sends out a signal, at 60Hz. That means that the display gets a new image every 1/60s. So you can measure an input lag of 17ms, 33ms, 50ms, 67ms, 83ms, etc. What you can't measure are input lags of 2ms, 5ms, or any other value... unless the testing methodology itself is unsound.
They're taking an average, but an average of what? "We have 20 pictures that show no input lag and 20 pictures that show 1 frame of lag. That makes the average lag half a frame = 8.3ms." If the margin of error (due to output synchronization) is 1 frame - and it is in my testing - then lag is either undetectable, ~1 frame, ~2 frames, etc.
It could very well be that the 245T has worse lag than other displays. I don't have access to most of the displays they've tested, and I don't have any CRTs. I can compare results to a 2407WFP or 3007WFP, or maybe a couple other LCDs. However, the baseline would be inherently different.
I talked about the question http://www.anandtech.com/displays/showdoc.aspx?i=2...">here and later http://www.anandtech.com/displays/showdoc.aspx?i=2...">here, and at that point I decided that the methodology and reliability (with clearly different screen refreshes taking place in pictures) made the whole process virtually meaningless, so I stopped doing it.
If you want a figure of approximate lag, I can try to put a number of frames "lag" with a margin of error of 1. So anything less than one is apparently "equal" - which is what I found in every test I tried previously. To do an average is misleading - or at least an abstraction that hides the inherent flaws in the testing methodology - so I won't do that.
nevbie - Tuesday, February 12, 2008 - link
I don't know if this is reasonable - but if I were to think a way to measure input lag, it wouldn't be a comparison of clone moded monitors where other is a CRT and other is the subject.Instead I'd like to measure the time difference between pressing a button (mouse/keyboard) and a change that occurs on the screen. This is what people care about anyway. Of course such measurement would also count all the other delays caused by system, not just monitor only. (Now that sounds interesting, at least from a gamer standpoint!)
How to do it? I don't know. A combination of a device that sends a signal to the PC and "photographes" the LCD (or part of it) would do it (constantly photographes for some time, after input given to the PC). Software-wise, a program that keeps the screen black and waits for input, and turns it red if it gets the input would be enough. Perhaps a modded caliberator could be used (dunno about their functionality). With such system you could even measure lag caused by other hardware, let's say multi-GPU (if such lag exists, that is).
Just my thoughts..
AnnonymousCoward - Tuesday, February 12, 2008 - link
I agree with your theory, that input lag measurements should be in increments of 1/60s. For some reason, that's never how the measurements play out.I found just what you asked for: 70 data points from 7 monitors, graphed. http://tinyurl.com/2gajok">http://tinyurl.com/2gajok http://tinyurl.com/rgx9n">http://tinyurl.com/rgx9n
Looking at the data, I think it's reasonable to take the average of 10 readings, in spite of unknown measurement inaccuracies. Those averages give pretty good information about the real-world lag versus a CRT.
Here's an easy test you can do to expose the lag: move your mouse across the screen in an abrupt, sharp sweep. Compare when the sound of the mouse against the table ceases, versus when the cursor stops moving.
jimmy43 - Thursday, February 7, 2008 - link
I tend to agree on most points with you. However, input lag IS a real issue. For example, I use a monitor with 16ms refresh time and it doesnt bother me at all, while it would drive other people nuts. The same goes for input lag, and certain people's sensitivies.Incidentaly, the 244T had input lag so terrible I read countless reports of them being returned because they were completely unusable. This is from many different sources on many different sites. So the first thing I wanted to know about the 245T was weather or not it addressed this issue.
If you could, at the very least, just throw something about it in the subjective area then that would be helpful.
JarredWalton - Thursday, February 7, 2008 - link
Subjectively, I didn't notice anything related to lag compared to other LCDs. But if I'm not susceptible to that.... :)JarredWalton - Thursday, February 7, 2008 - link
And I added a note on the subjective evaluation for you.PPalmgren - Friday, February 8, 2008 - link
Input lag is the main thing I look for in LCD monitor reviews, and no one seems to want to cover it. It is the ultimate buying point for me. I "upgraded" from a Viewsonic VX922 to a NEC 2470WNX and the input lag made me put my 19 inch back of my desk. I mainly play RTSes and clicking accuracy is very important. When using the WNX I had major problems because of the delay, destroying my ability to click accurately on small things at high speed. In order to click dead-on, you have to guess your mouse distance exactly and click before the pointer shows up there on the screen. The input delay feels to be about 2-3 frames difference between my monitors. I currently have them both hooked up and use nView to switch between them now.Would it be possible to set a computer up for dualview and compare reviewed monitors side-by-side with a known well performer to measure input lag through a photo, etc? I think it would be a great thing for reviews. Since my purchase I've built 2 machines for customers who wanted 24'' monitors, and I've tested each of them with the same results (HP2408, Dell2407).
jimmy43 - Thursday, February 7, 2008 - link
I tend to agree on most points with you. However, input lag IS a real issue. For example, I use a monitor with 16ms refresh time and it doesnt bother me at all, while it would drive other people nuts. The same goes for input lag, and certain people's sensitivies.Incidentaly, the 244T had input lag so terrible I read countless reports of them being returned because they were completely unusable. This is from many different sources on many different sites. So the first thing I wanted to know about the 245T was weather or not it addressed this issue.
If you could, at the very least, just throw something about it in the subjective area then that would be helpful.
LTG - Thursday, February 7, 2008 - link
Good intro on the base panel technologies.It would be interesting to know what is used for most LCD TVs (52", 65").
I don't notice it mentioned usually.