Does respone time really matter?

[kinsonapril]

What I am going to say is just base on my understanding of the response rate, they might be wrong, please help to correct it!

Here's what I think:
As I have read the technical guide from tweakguides, LCD monitor response time is kind of equal to refresh rate. In order words, a 16ms means: in one full second, the lcd monitor can refresh all the pixels on the screen 1000/16 = 62.5 times, which equivalent to 62.5Hz refresh rate.

So, simply saying, a 8ms LCD monitor got a 125Hz refreshrate. But as most of the LCD monitor in the market has preset the refresh rate to 60Hz in most of the resolution (e.g. 1280x720, 1680x1050) which means, even the monitor got 8ms response time, because of the restrict of the manufacturers preset Max refresh rate, the monitor basically can't operate at 8ms(125Hz) but only somewhere around 16ms as it is equal to 60Hz.

I have done some reserach and I found that the LCD monitors which have a response time lower than 16ms (e.g 8ms, 5ms) are also set to be 60Hz or 75Hz.
So in general, isn't a 16ms is enough for almost everything?

That's what I thought, I would like to ask you guys, is that correct? Or I totally misunderstand it all?? May be a lower response time affect other aspect of a LCD performance??

And the last question is, people always say 8ms will have less ghosting than a 16ms, so, "IF" what I wrote was correct, that means both of them should be operating at a same refresh rate (e.g. 60Hz), as if refreshrate = response time, aren't they both operating at 16ms?@@? Then how can the ghosting become less in the 8ms monitor?


Thx for reading and sorry for my bad English! I am from HK.

 

[meanstreak]

I don't know what to tell you on your technical question.

In real world...

I have Samsung 940bf with 2ms response and don't see diffrence in response between my and friends 8ms lcd. ( only in picture quality).

Other friend has a 12ms Phillips LCD and looking at it seems the same as looking on athletics photo finish on TV

 

[NoxTek]

Response time has absolutely nothing to do with refresh rate.

Response time is the amount of time it takes for a single pixel (not the entire panel) on an LCD to go from black to white and then black again. Or as some manufacturers have started padding their ratings, gray to black to gray again. The higher the response time, the longer it takes for an open (white or active) pixel to reach a closed (black or inactive) state. This characteristic of LCD panels is what leads to the 'ghosting' effect which is so undesireable when these panels are used for gaming and/or entertainment purposes. A LCD panel with a high response time is going to be horrible for gaming or a movie with a fact action scene because it will constantly be showing brief 'afterimages' and motion trails on bright objects as the LCD panel tries to keep up with the fast action. The refresh rate of the rasterized data being fed to the monitor matters not - it could be 30hz and the pixels on the LCD are still going to have the same response time characteristics.

You could easily have a 25ms LCD panel being fed video at 100hz, but it would look horrid.

So why don't our modern 'gaming' LCDs have the ability to handle higher refresh rates? Good question... this is a problem that has plagued many of us. Right now the main difficulty is the limiting factor of a single link DVI connection, which most LCD panels under 24" use exclusively. A single link DVI connection has a limited amount of bandwidth and when you increase the refresh rate you drastically increase that bandwidth. (This wasn't an issue with older analogue VGA connections)

A case in point: A single-link DVI connection is limited to roughly 3.7gbit a second. Your average 20" - 22" widescreen LCD monitor has a native resolution of 1680x1050 and at 60hz that's just under the 3.7gbit/second bandwidth cap for single-link DVI. So the 60h limitation is really the nature of the beast when dealing with single link DVI.

So as we see newer displays develop that use dual-link DVI hopefully we will see the capability to handle higher refresh rates get incorporated into the electronics that drive the panels. A 24" widescreen that has a 2ms response time and can handle 1680x1050 at 100hz? That's my dream 'gamers monitor'.

 

[kinsonapril]

Thanks, Blue Falcon. Your answers make me understand more though I still not getting it all!

I wanna ask one more question. Does response time affect page tearing issue? Will it be a possibility that a game have page tearing on a 16ms LCD but not/less on a 8ms?

 

[BlackTigers91]

Well, I don't think it matters a whole lot, and I feel that people exaggerate quite a bit on having a low response time, and ghosting. I say this because I have a 15" LCD panel, with a 23ms response time, and through multiple games, I have yet to notice any ghosting. So....

 

[NoxTek]

Thanks, Blue Falcon. Your answers make me understand more though I still not getting it all!

I wanna ask one more question. Does response time affect page tearing issue? Will it be a possibility that a game have page tearing on a 16ms LCD but not/less on a 8ms?

No, to put it in laymans terms 'tearing' is a result of the refresh rate not exactly matching the frames per second of the video being displayed. This is why the video drivers for your graphics card have a vsync (vertical sync) setting.

Say you've got an LCD at 60hz and your graphics card's driver has vertical sync disabled. Now let's say you are running a fast paced game of quake 3 on a really powerful card like a 7900GTX. That game is going to run as many frames per second as the game engine allows (I think for Q3 it's 125fps) but the monitor is still only going to be refreshed 60 times a second (60hz). What you witness is horrible 'tearing' (disjointed horizontal pieces of the video image) as the game tries to send 125 frames per second to a display that's only being updated 60 times a second.

Enabling vsync fixes all of that - it locks the FPS rate at 60 frames per second or below - matching the monitor's 60hz refresh rate. No more tearing.

There are pitfalls to vsync which I won't get into here, but for most people vsync enabled is the preferred choice when you want a smooth gaming experience.

 

[larkin]

You ask a good question of why the apparent refresh "delay" doesn't overwhelm or make inpercievable, visual improvement of sub 16ms responce times. Refresh rate is the number of times per second that a pixed is asked to take on a certain color value. Responce time is a measure of the time it takes that pixel to "turn" that color. So if you are looking at a screen of all black and the next refresh requests all white, it takes your 16ms (black to white) pannel 16ms to turn white from the time it was requested to. As you pointed out 16 ms is also about 60 refreshes/sec, so this means that if the next refresh then asks the monitor to turn black again, those pixels still may be in the process of turning white, thus a grey'd effect may happen. You could say your effective refresh rate is refresh delay + responce time, however it's not exactly like that. Ghosting is caused by slow responce time for the same reason, one refresh still has reminents of the old refresh's colors.

Responce time, like much else, is only as important as the perception of the user. For many, they swear they don't see ghosting at 16ms, for others, even 8ms doesnt hide the effect enough. Personally, the samsung 940BF series was the best lcd i have ever seen with regard to ghosting, it was CLEARLY better. However, high res monitors dont yet have the capability of such low responce times so I use my samsung which has a nice responce of 8ms and is a great widescreen. So yeah, that should clear things up.. go to best buy or something to look and judge for your self.

 

[artmonkey]

I too think these low responce times are meaningless. I would love to test it on a bunch of LCDs next to each other though. I have used several LCDs in the past and always played games on them (never next to each other though unfortunately) I've gone from 25ms down to about 2 and there doesn't seem to be any difference. It'll be interesting to see if BenQ's BFI technology does anything to improve thsighosting effect but at the moment it's still untested.

I also agree that a faster refresh would be nice, I guess they'll just have to use Dual Link DVI cables but is this enough for some screens? I think the limit of Single link is 1920x1200 @ 60Hz. As far as I can tell a dual link DVI contains enough bandwidth for 1920x1200 @ 120Hz. These cables are used with higher resolution monitors like the Apple/Dell 30" screens for 2560x1600 @ 60Hz but if you want a higher refresh at this resolution then we'd need yet another digital cable standard =(. Using more than 24bit colour would also be nice if it was supported in future LCD screens somehow but we would need a 64bit colour option in the graphics card... Eek!!!

 

[joemama]

Yes and no. You wouldn't want to use a professional graphics monitor that has a 25ms response time for gaming but then again a 5ms TN panel is going to suffer from poor viewing angles and lack of color accuracy. There are many people (myself included) who are perfectly happy gaming on a 16ms Dell 2007FPW...but then again in real world testing, the actual response time has been found to be closer to the 6ms NEC 20WMGX2. If response time/refresh rate and ghosting are really a great concern....then maybe an lcd panel is out of the question.

 

[the gamer]

Anything under 16ms is considered good, any more you will start to see ghosting effect (double vision sort of).

 

[artmonkey]

Yes and no. You wouldn't want to use a professional graphics monitor that has a 25ms response time for gaming but then again a 5ms TN panel is going to suffer from poor viewing angles and lack of color accuracy. There are many people (myself included) who are perfectly happy gaming on a 16ms Dell 2007FPW...but then again in real world testing, the actual response time has been found to be closer to the 6ms NEC 20WMGX2. If response time/refresh rate and ghosting are really a great concern....then maybe an lcd panel is out of the question.

As I said, I have used a 25ms monitor for gaming and it looked better than the 2ms one I use at work now. Have you actually used a 25ms LCD for games or is this something you've heard? Because I hear a lot of people say this without having actually tested it for themselves. I think this low response time shenanigans is just a marketing gimmick to sell low end screens to gamers.

 

[NoxTek]

As I said, I have used a 25ms monitor for gaming and it looked better than the 2ms one I use at work now. Have you actually used a 25ms LCD for games or is this something you've heard? Because I hear a lot of people say this without having actually tested it for themselves. I think this low response time shenanigans is just a marketing gimmick to sell low end screens to gamers.

At any one time I've got 15 or 20 different flat panels laying around (I buy 'em used cheap when they come up). Most of them are 25ms units used in various workstation environments and let me tell you the difference between a 25ms and a 16ms when gaming is staggering. The difference between 16ms and 8ms is not so staggering but it IS quite noticeable. Below 8ms and the differences are much much more subtle and are only barely noticeable in the most fast paced and colorful of games. In my opinion 8ms is a decent response time and anything lower is just a bonus.

Oh and the games I speak of are hardcore first person shooters mostly. You're not going to be able to tell the difference in an older 25ms panel and a new 2ms gaming panel if you fire up a game of Age of Empires or something... except the contrast ratio and overall brightness is bound to be lower on the older 25ms panel.

 

[larkin]

yepp, 25->16ms = huge difference. I dont suppose anyone bothered to read my post but this is the case because in a 60htz refresh lcd, a 25ms responce screen takes two refreshes to actually take on the correct color.

 

[kinsonapril]

Thanks a lot to all !!! I understand more!! Especially from larkin's reply!!

I got three question left:

1. Does "Screen Tearing" related to response time? Slow respone time = more tearing? Fast Response Time = less/no tearing?

2. Does "Screen Tearing" happen when FPS is lower than Refresh rate? If it does, what kind of situation? with v-sync on/off ?

3. Possible to have tearing while watching DVD moives? (I heard that FPS of a moive is constant about 30 FPS, though I might be wrong...)

Thanks~!!

I concern about tearing the most, it looks worse than ghosting to me And I got quite a lot of tearing while play xbox360 BlueDragon but there are people saying no tearing at tall.. strange to me and so I start think is my 2007WFP problem...

 

[Greenwit]

Anything under 16ms is considered good, any more you will start to see ghosting effect (double vision sort of).

You will see ghosting with as little as 8 ms. That's the response of the LCD I'm typing on now (see sig). Compared to the other CRT in my sig, the ghosting and smearing is pretty obvious. You won't know the difference unless you own a good CRT and neither will you notice with a slow system. My system, with my two monitors (LCD and CRT) the difference is not minor. In fact, play FEAR on that NEC that I have and going to the Sammy is a bit painful. Unfortunately, CRTs have been out of circulation for too long now and most people haven't owned a good one for years (if ever). For them, they have no way to knowing the gap that exists which is too bad.

 

[Sycraft]

Response time does matter, but only to a point. In theory, 16ms is about the maximum useful response time with an LCD that runs at 60Hz since that is as often as it receives updates. However the thing to realise is that response time isn't consistent across the brightness range. Some transitions are faster than others. Well of course manufacturers usually are reporting their best time, so just because a display can do 16ms at it's best doesn't mean it's that good the whole range over.

For example VA type panels tend to be the fastest going all the way black to all the way white and the slowest going from black to dark grey. I do notice this on my VA panel (FP241W). In games like WoW there is no ghosting that I can see at all, ever. In FEAR, which is real dark, I can occasionally see a bit of ghosting. I have to look for it or I don't notice as it's pretty minimal, but it's there.

So while you don't want to get a slow monitor, worrying about getting an overly fast one probably isn't useful. I can't tell you what the cutoff is. In general, I think if you get a high quality modern display, it'll be fast enough that it's not a problem.

 

[omega-x]

the best way to test ghosting is to try to read text that scrolls across or down a screen.

CRTs are clear and readable
LCDs are more so 'motion blur' than 'ghosting' these days.

 

[larkin]

Response time does matter, but only to a point. In theory, 16ms is about the maximum useful response time with an LCD that runs at 60Hz since that is as often as it receives updates.

that's completely inaccurate. Why dont people read the rest of the replies before posting their own... there has got to be a name for that right?

 

[kinsonapril]

larkin, I have post 3 more questions on the previous reply, could you help me on it?

thanks

 

[larkin]

larkin, I have post 3 more questions on the previous reply, could you help me on it?

thanks

shearing doesnt have to do with fps matching the refresh it has to do with the refresh being out of sync with the fps. As far as I know, the LCD does a vertical refresh line by line, if the render'd frame is not in sync then what can happen is that the first half of the refresh could be from frame 1 and then the 2nd half of the refresh is from frame 2. this can happen at any fps. This can also happen with video playback although if you see it happening with video playback then the problem is bad drivers. Some forceware drivers were just really bad for video playback, when i upgraded the drivers the video was smooth again.

I hate tearing too so I always run with vsync forced on and tripple buffering. while tearing is an issue, it shouldn't influence what monitor you get because you can always turn vsync on.

 

[NoxTek]

As far as I know, the LCD does a vertical refresh line by line,

Although the pure technology of an LCD panel gives the possibility of not having any rasterization of the video being displayed (ie the ability to drive each pixel separately), LCD monitors in their current form still render in a horizontal rasterization - horizontal line by line. This is due to the electronics driving the panel and how they interface with your PC. This is probably the way it will be done for the forseeable future.

Why is it done this way? My guess is that it's a holdover from the way video images have always been rendered by a display device. Even the earliest CRT tubes in the early 1900s used a horizontally rasterizing electron beam, lighting up phosphors line by line.

 

[NoxTek]

Thanks a lot to all !!! I understand more!! Especially from larkin's reply!!

I got three question left:

1. Does "Screen Tearing" related to response time? Slow respone time = more tearing? Fast Response Time = less/no tearing?

Again, tearing and response time have nothing to do with each other. Nothing. Absolutely nothing. OK?

2. Does "Screen Tearing" happen when FPS is lower than Refresh rate? If it does, what kind of situation? with v-sync on/off ?

If vsync is disabled screen tearing can certainly happen wether the frames per second is higher or lower than the refresh rate. It will happen so long as the frames per second doesn't exactly match the refresh rate.

Vsync (vertical sync) fixes that by making sure the frames per second is always equal to or a divisor of the refresh rate. Assuming your refresh rate is 60hz then with vsync enabled your graphics card will only output rates of 60fps (1/1), 30fps (1/2), 20fps (1/3rd), 15fps (1/4th), 12fps (1/5th), etc.

You can avoid the divisor issue with vsync by enabling triple buffering, but that's a discussion that threatens to go outside the scope of this thread.

3. Possible to have tearing while watching DVD moives? (I heard that FPS of a moive is constant about 30 FPS, though I might be wrong...)

Normally no, never any tearing while watching DVD movies or any video actually. The only time this happens is with an improper driver installation, improper codec installtion, or improper video acceleration settings. If things are set up properly you should never see tearing when watching a DVD/video on your PC.

I concern about tearing the most, it looks worse than ghosting to me And I got quite a lot of tearing while play xbox360 BlueDragon but there are people saying no tearing at tall.. strange to me and so I start think is my 2007WFP problem...

If you are using your Xbox 360 with an LCD monitor you could definately be experiencing a tearing issue. There are all kinds of weird quirks when interfacing the Xbox360 with an LCD monitor. I would think that the Xbox 360 would be intelligent enough to cap the framerate at 60fps when connected to a 60hz display, but who knows? Maybe a future update from Microsoft will fix it. *shrug*

 

[kinsonapril]

Thanks a lot Blue Falcon !! Very clear answer from you!!

I got one last thing which I am still not sure. The following message is quoted from an article about "page tearing" from teamxbox:

Chris Satchell: Users are correct; “Page tearing” is an artifact of changing the displayed frame of the game while the display device is partially through displaying the previous frame. Games normally choose to wait for the v-sync signal from the console to know that it is safe to swap to the new game frame in a way that will not be perceived by users. Often there is some dead-time while waiting for the v-sync signal; a buffer to make sure the game always is ready at the right time. Some games choose to cut the timing extremely tight to get more into each game frame and if for any reason a frame is not ready for the v-sync they change the frame anyway. This can result in a visual tear, but means the game-play remains smooth with no jitters. Other games decide to run a maximum consistent frame-rate that does not match exactly to the v-sync patterns this can result in higher fidelity control, but with occasional tearing (the vast majority of frames are absolutely fine).
http://features.teamxbox.com/xbox/1607/Xbox-360-VSync-Issues-Demystified/p1

You said v-sync ensure the FPS equal to or a divisor of the refresh rate. So, if the FPS is 30fps with v-sync enabled, page tearing won't happen anyway(on a 60Hz LCD)?

Then, that sentence(in red) is incorrect?

Thanks! You really help me a lot!

 

[larkin]

is it just me or are these questions getting a little crazy?

how about you turn v-sync on and stop obessing about some obscure case where visual perfection will falter for a fraction of a second. what is the decision you are trying to make here? LCD vs CRT? I believe me and the other users have given you enough info about lcd refresh, responce time and tearing for you to make your own discissions now with regard to this topic.