simple question on response time is it display lag?

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chrcoluk

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TN is supposedbly the fastest for LCD.

However on the 3 TN monitors I have owned (one been a laptop screen) I have the same issue on all 3. That is moving black has a shadow trail behind it (lag). Whether it be mouse pointer, scrolling text or dragging a window around. What is this lag? it is visible and noticeable.

On my old PVA screen (now dead) I had the same, some lag but was less noticeable.

On my dell e-ips (2209wa) this lag is almost non existant and feels like a CRT in that respect.

So the lag I am describing is it response time? if yes then it seems to indicate published response times mean very little.
 
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According to LG, IPS has a more repeatable response time across transitions than TN or PVA. Otherwise, the TN panels you are using could be older or have poor overdrive.
 
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In general TN has a very fast pixel transition time; but can be slow if it's unaccelerated using Response Time Compensation/Acceleration techniques.

A "5ms" panel without RTA is approximately 20-30ms in actual use in many transitions. However a "2ms" panel with a good RTA function will actually perform all transitions usually under 12ms; well less than one frame; so you see no blur or artifacting (other than edge halos, etc). So you see that even with what's supposed to be the fastest type of panel; it may or may not be all that fast due to the addition of RTA. Your laptop may not have any RTA function; or a particularly slow and older 8ms unacclerated TN panel.

If the trails you see are like light halos (very bright; like a shadow on the glass), then this can be part of a poorly designed RTA function (what's called "overshooting"). This can be considered somewhat normal. If you see a visibly blurred and dark shadow behind the cursor, then the panel is just plain slow. It almost certainly does not use RTA.

PVA panels are different. They have a particularly slow matrix type (original VA); and may be coupled with RTA mechanisms that grossly overshoot and produce all sorts of artifacts; including red/blue shadows and smearing colors. Newer S-PVA/C-PVA tech is better; and MVA panels used in TV's can be quite good (but input lagged).

E-IPS is all around good and usually has RTA (at least as an option in the OSD). The slowest transitions on E-IPS or S-IPS are approx 16ms or less. This can be good enough that you won't see artifacts or much blurring (one frame = 16.7ms). If measured head to head; E-IPS is not as fast as a 2ms panel; but damn close due to the "way it feels", including the lack of pixel smearing; low input lag; and general responsiveness. The matrix type has crystals arranged in such a way that many color transitions are easier/faster than other panel tech.

So to answer your question; no the lag you see is response time; not input lag. Input lag is a total system lag from mouse movement to on screen response and a slow panel or the image processing in your panel contributes to this.
 
lawless2142 said:
E-IPS is all around good and usually has RTA (at least as an option in the OSD). The slowest transitions on E-IPS or S-IPS are approx 16ms or less. This can be good enough that you won't see artifacts or much blurring (one frame = 16.7ms). If measured head to head; E-IPS is not as fast as a 2ms panel; but damn close due to the "way it feels", including the lack of pixel smearing; low input lag; and general responsiveness. The matrix type has crystals arranged in such a way that many color transitions are easier/faster than other panel tech.
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IPS is described as the slowest of all LC modes and PVA as the fastest. it is odd that the reverse is true in modern designs.
 
The OP sounds like he's describing refresh rate. 120Hz monitors correct these issues.
 
its not due to refresh rate, my e-ips only runs at 60hz.

lawless2142 explanation seems to make sense, my TN monitor is quite old now, got it 4 or so years back, laptop not so old but was hardly cutting edge when I got it (free with phone contract).
 
chrcoluk said:
TN is supposedbly the fastest for LCD.

However on the 3 TN monitors I have owned (one been a laptop screen) I have the same issue on all 3. That is moving black has a shadow trail behind it (lag). Whether it be mouse pointer, scrolling text or dragging a window around. What is this lag? it is visible and noticeable.

On my old PVA screen (now dead) I had the same, some lag but was less noticeable.

On my dell e-ips (2209wa) this lag is almost non existant and feels like a CRT in that respect.

So the lag I am describing is it response time? if yes then it seems to indicate published response times mean very little.
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Yes, it is response time. But that's not really the full answer.

TN panels have the best response time, but they're poor in quality and tend to have issues that appear as if they have a high response time.

PVA panels are partly known for a bug that caused them to appear as if they had a very high response time, but it was just that. It was fixed in 2007.

IPS panels are of somewhat higher quality than even the PVA panels, but I actually find myself preferring PVA.

It comes down to the person. I don't notice the dark lag anymore (the effect of the pixels responding to the input from the computer and changing color too slowly).. I think you're just focusing on it too much.
 
Taer said:
PVA panels are partly known for a bug that caused them to appear as if they had a very high response time, but it was just that. It was fixed in 2007.
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A bug?? VA panels still have high response time for certain transitions.

I don't think the OP is focusing on it too much. He was simply asking a question and he is 100% correct in saying published response times mean very little.
 
Taer said:
Yes, it is response time. But that's not really the full answer.

TN panels have the best response time, but they're poor in quality and tend to have issues that appear as if they have a high response time.

PVA panels are partly known for a bug that caused them to appear as if they had a very high response time, but it was just that. It was fixed in 2007.

IPS panels are of somewhat higher quality than even the PVA panels, but I actually find myself preferring PVA.

It comes down to the person. I don't notice the dark lag anymore (the effect of the pixels responding to the input from the computer and changing color too slowly).. I think you're just focusing on it too much.
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its very obvious, hard to not notice it :)

thankfully I rarely use the TN monitor and I just put up with it on laptop.
 
yes I am aware of it but dont go looking for it. not sure what you trying to say there. I am aware of it due to how much it stands out. But regardless my question is answered, in that the claim that TN's are always faster doesnt appear to be true but I am comparing my earlier gen TN to later gen e-IPS.
 
TN panels aren't the fastest. They are only fast for certain gray-to-gray transitions. Manufacturers started using gray-to-gray measurements so they could claim lower response times on TN panels. As you've seen, TN panels are actually pretty slow with dark objects moving against light backgrounds, and without overdrive, some transitions are in the 25-30 ms range. Overdrive (response time compensation) is designed to reduce that, but how well it works depends on the implementation.

IPS panels are the opposite. They're faster with dark objects moving against light backgrounds, but they're slower for light objects moving against dark backgrounds, but even without overdrive, transitions never exceed 25 ms. Overdrive helps reduce the slower transitions to below one frame, making them almost as fast as a TN panel for gray-to-gray transitions.

VA panels are horribly slow with gray-to-gray transitions, and without overdrive, some transitions exceed 50 ms. The only way to compensate for that is to buffer frames to determine how much overdrive to apply, so either you have too much ghosting or too much lag, and when the overdrive implementation is bad, you can end up with both.

Basically, TN with overdrive and IPS with overdrive are the fastest, with TN being slightly faster for certain gray-to-gray transitions and IPS being slightly faster for other transitions.

You can usually tell if a monitor has overdrive or not based on the response time specs:

5 ms = TN without overdrive
2 ms = TN with overdrive
1 ms = TN with bullshit

6-8 ms = IPS with overdrive
12+ ms = IPS without overdrive

VA panels almost always have overdrive these days, but the overdrive in the 3000:1 contrast VA monitors is not good enough to compensate for the poor gray-to-gray response times, which is probably why they don't lag like the ones with better overdrive.
 
ToastyX said:
5 ms = TN without overdrive
2 ms = TN with overdrive
1 ms = TN with bullshit

6-8 ms = IPS with overdrive
12+ ms = IPS without overdrive
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When Sycraft talks about "forming pixels" and "ISO time", are those different (more difficult) than "response time"?

Sycraft said:
The main issue is that I don't think IPS is fast enough right now. For 120Hz you have to have pixels formed in 8.3ms. While IPS displays with overdrive can get some transitions faster than that, they can't get all. I think 12ms is the fastest ISO time I've seen. Means they just aren't fast enough to pull 120Hz.
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http://hardforum.com/showpost.php?p=1036205770&postcount=12
 
ToastyX said:
TN panels aren't the fastest. They are only fast for certain gray-to-gray transitions. Manufacturers started using gray-to-gray measurements so they could claim lower response times on TN panels. As you've seen, TN panels are actually pretty slow with dark objects moving against light backgrounds, and without overdrive, some transitions are in the 25-30 ms range. Overdrive (response time compensation) is designed to reduce that, but how well it works depends on the implementation.

IPS panels are the opposite. They're faster with dark objects moving against light backgrounds, but they're slower for light objects moving against dark backgrounds, but even without overdrive, transitions never exceed 25 ms. Overdrive helps reduce the slower transitions to below one frame, making them almost as fast as a TN panel for gray-to-gray transitions.

VA panels are horribly slow with gray-to-gray transitions, and without overdrive, some transitions exceed 50 ms. The only way to compensate for that is to buffer frames to determine how much overdrive to apply, so either you have too much ghosting or too much lag, and when the overdrive implementation is bad, you can end up with both.

Basically, TN with overdrive and IPS with overdrive are the fastest, with TN being slightly faster for certain gray-to-gray transitions and IPS being slightly faster for other transitions.

You can usually tell if a monitor has overdrive or not based on the response time specs:

5 ms = TN without overdrive
2 ms = TN with overdrive
1 ms = TN with bullshit

6-8 ms = IPS with overdrive
12+ ms = IPS without overdrive

VA panels almost always have overdrive these days, but the overdrive in the 3000:1 contrast VA monitors is not good enough to compensate for the poor gray-to-gray response times, which is probably why they don't lag like the ones with better overdrive.
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Very informative post - thanks.
 
ToastyX said:
TN panels aren't the fastest. They are only fast for certain gray-to-gray transitions. Manufacturers started using gray-to-gray measurements so they could claim lower response times on TN panels. As you've seen, TN panels are actually pretty slow with dark objects moving against light backgrounds, and without overdrive, some transitions are in the 25-30 ms range. Overdrive (response time compensation) is designed to reduce that, but how well it works depends on the implementation.

IPS panels are the opposite. They're faster with dark objects moving against light backgrounds, but they're slower for light objects moving against dark backgrounds, but even without overdrive, transitions never exceed 25 ms. Overdrive helps reduce the slower transitions to below one frame, making them almost as fast as a TN panel for gray-to-gray transitions.

VA panels are horribly slow with gray-to-gray transitions, and without overdrive, some transitions exceed 50 ms. The only way to compensate for that is to buffer frames to determine how much overdrive to apply, so either you have too much ghosting or too much lag, and when the overdrive implementation is bad, you can end up with both.

Basically, TN with overdrive and IPS with overdrive are the fastest, with TN being slightly faster for certain gray-to-gray transitions and IPS being slightly faster for other transitions.

You can usually tell if a monitor has overdrive or not based on the response time specs:

5 ms = TN without overdrive
2 ms = TN with overdrive
1 ms = TN with bullshit

6-8 ms = IPS with overdrive
12+ ms = IPS without overdrive

VA panels almost always have overdrive these days, but the overdrive in the 3000:1 contrast VA monitors is not good enough to compensate for the poor gray-to-gray response times, which is probably why they don't lag like the ones with better overdrive.
Click to expand...

QFT, very insightful. Well said, you should work and answer for wikianswers, yahoo answers, and answers.com :D
 
ToastyX said:
TN panels aren't the fastest. They are only fast for certain gray-to-gray transitions...
IPS panels are the opposite. They're faster with dark objects moving against light backgrounds, but they're slower for light objects moving against dark backgrounds, but even without overdrive, transitions never exceed 25 ms. Overdrive helps reduce the slower transitions to below one frame, making them almost as fast as a TN panel for gray-to-gray transitions...
Click to expand...

ToastyX, based on this information, what's your opinion on e-IPS 120hz (i.e. 3D capable) monitors? Do you think the current e-IPS panels with the right panel driver and decent implementations of overdrive could do just as good a job of avoiding cross-talk / 3D as the current '2ms' TN panels being used for 3D monitors? How about in 120hz non-3D mode, do you think e-IPS are capable of showing 120 discrete frames per second (i.e. most color transitions would need to happen inside a 8ms window)?
 
sethk said:
ToastyX, based on this information, what's your opinion on e-IPS 120hz (i.e. 3D capable) monitors? Do you think the current e-IPS panels with the right panel driver and decent implementations of overdrive could do just as good a job of avoiding cross-talk / 3D as the current '2ms' TN panels being used for 3D monitors? How about in 120hz non-3D mode, do you think e-IPS are capable of showing 120 discrete frames per second (i.e. most color transitions would need to happen inside a 8ms window)?
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For 3D, I'm not sure because even 2 ms TN panels are still not fast enough to completely avoid crosstalk. I think IPS with good overdrive can do a better job overall, but even if all transitions were under 8 ms, you'd still see crosstalk during the time the pixels are transitioning. What's really needed is to get all transitions under 8 ms, then scan the backlight in such a way so the pixels are only lit after the transition completes, which would also get rid of the sample and hold effect.

For non-3D mode, it's irrelevant because even if the response times couldn't quite keep up, you would still benefit from 120 Hz. Frame rates for movies would be evened out, games would have less tearing, and you'd still see the smoothness over 60 Hz. The worst that would happen is there would be a little bit of blurring.

120 Hz IPS panels already exist in HDTVs. People don't consider them true 120 Hz because they don't accept 120 Hz input, but the panels themselves are true 120 Hz, and the interpolation produces 120 real frames per second. HDTVs aren't designed to accept 120 Hz signals because TV signals are not 120 Hz, and 120 Hz input would also require dual-link DVI or DisplayPort, which HDTVs don't have.

I think the bigger problem is the sample and hold problem, which hasn't been properly addressed in LCD monitors. Each frame persists in your eyes for 10-15 ms, and when following motion, the image that persists in your eyes mixes with the image that's still on the screen, causing a blurring effect. CRT monitors don't have that problem because the image is only on the screen for a split second, but LCD monitors keep the image on the screen until the next refresh. On top of that, the pixels take time to transition, so your eyes see that as well. Having a higher refresh rate reduces the holding period, but what's really needed is higher refresh rates + good overdrive + proper backlight scanning, which no monitor seems to do. That is why even the fastest LCD monitors still have some motion blur compared to a CRT monitor. Even if IPS couldn't keep up with 120 Hz, 85 Hz without the sample and hold effect would still be a huge improvement over current 60 Hz monitors.
 
I hope we do see some more 120hz monitor announcements at CES, and an IPS 120hz monitor would be awesome.

Regarding the sample and hold effect, most of the '240hz' TVs are using a scanning backlight + 120hz panels in the manner you describe if I remember correctly, in fact I think I remember a scanning backlight 60hz monitor review before (Benq?) so a 120hz + scanning backlight + IPS monitor would be pretty awesome.
 
ToastyX said:
6-8 ms = IPS with overdrive
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Actually that would be "5-8 ms = IPS with overdrive". My Planar PX2611w is "rated" at 5ms. It probably uses slightly more aggressive RTC than my NEC LCD2690WUXi, but I don't notice any ill effect.
 
sethk said:
Regarding the sample and hold effect, most of the '240hz' TVs are using a scanning backlight + 120hz panels in the manner you describe if I remember correctly, in fact I think I remember a scanning backlight 60hz monitor review before (Benq?) so a 120hz + scanning backlight + IPS monitor would be pretty awesome.
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I don't know how the TVs do it, but the BenQ monitor did the opposite of what needs to be done. It blanked out a line instead of lighting up a line, which doesn't solve the problem, especially with the slower response times of VA panels. It barely reduces the visible holding period, so it doesn't mask the slow response times, and while the motion blur would be reduced, the holding period is still there, so you end up with a double-vision effect. Scanning the backlight at 60 Hz can also cause visible flickering.

The backlight needs to be scanned like a CRT, showing only a small section at one time, and it needs to be done at a higher refresh rate to reduce flickering, and the response times must be fast enough so the transition is complete by the time the section is lit. Only then will an LCD monitor get anywhere close to CRT-like motion.

JaguarSKX said:
Actually that would be "5-8 ms = IPS with overdrive". My Planar PX2611w is "rated" at 5ms. It probably uses slightly more aggressive RTC than my NEC LCD2690WUXi, but I don't notice any ill effect.
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I didn't see any evidence of overdrive on the Planar PX2611W, and the same applies to the identical DoubleSight DS-263N. I didn't see any overdrive artifacts on those monitors, which could have been due to a perfectly-tuned overdrive, but after comparing with the Dell 2209WA, it was obvious there wasn't any overdrive at all because there was no improvement with light objects moving against dark backgrounds. The motion on those monitors is more like the NEC EA231WMi, which is rated at 14 ms.

The overdrive option on the NEC 2690 also barely had any effect, unlike the NEC 2490 where I could see clear evidence of overdrive. I would have to check the NEC 2690 again now that I know what to look for.
 
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