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Input Lag, Or Why Faster Isn't Always Better
mr_sifter writes "LCD monitor manufacturers have constantly pushed panel response times down with a technique called 'overdrive,' which increases the voltage to force the liquid crystals to change color states faster. Sadly, there are some side effects such as input lag and inverse ghosting associated with this — although the manufacturers themselves are very quiet about the subject. This feature (with video) looks at the problem in detail. The upshot is, you may want to test drive very carefully any display boasting low integer millisecond pixel response times."
First, we have to look for monitors with 6bit or 7bit color instead of 8 per channel, now we have to start testing for overdrive voltages? Buying an LCD is becoming a real pain in the arse.
These terms 'response time' and 'contrast ratio' are checklist items. What matters is how the display looks and feels. As long as we continue to insist on checklists as a means of determining what to buy, manufacturers are going to keep using tricks like overdrive to make their checklists look better and better.
At the end of the day, sadly, this means that you can't just look at a checklist when buying an LCD display. You must test drive a model live before considering its purchase.
My blog
You really should test drive ANY display before you buy it. Or at least read a lot of reviews from reliable sources.
I actually read the entire article. Pretty interesting. I didn't know about the three major LCD technologies, etc.
It's slightly frustrating when companies "decline to comment."
First of all, I'm not really sure why that's considered a "upshot." But more importantly, I baffled by the submitters implication that I would have to carefully test an 8ms lag screen but not a 7.5 or 8.2ms screen. Huh?
A slashdotter who didn't build his own computer is like a Jedi who didn't build his own lightsaber.
was when I fire up Outlook and start typing a new email, and nothing shows up on the screen for 10 seconds
Do plasma displays have this same issue?
http://www.anthonyw.net
I really thought this was common knowledge.
When I bought my Eizo LCD last summer, the first thing I did was read around. These issues came up immediately.
Long story short: Prad was my friend.
Rotaluclac
reminds of my time making CDROM drives when we ere chasing 4x, then 8x, then 16x, then...
never mind the fact that the interface at the time could not handle the high speeds were were getting too so they were totally pointless, the effort was still to physically read some data off the outer edge of the disc at the quoted speed so we could sell the unit and keep up with the arms race.
I now purposely buy technology a few years old, just so they can work the bugs out and I can ensure it is fully supported under all operating systems, it is rare indeed that I adopt early.
any technology arms race will promote one specific feature above all others and rarely end up with a device that is fit for market and a well rounded balance of features - though I grant that there are some exceptions.
what i had to do. i have a camera pointed at my monitor as we speak and i am working on a script to move the mouse in accordance with the stock market movement. inverse ghosting will allow me to see the mouse trail from the immediate future and place my bets accordingly. i am only posting this because i am looking for an investor. as soon as the market makers realize what is happening they will delay all online tickers by just enough to remove the inverse ghosting effect, so it is imperative that the first trades be made with a huge BANG. pleaes write me at madmadgenius@gmail.com if you are interested. serious investors ONLY
Dell screens have 'desktop', 'media', and 'gaming' modes, which (I guess) affect colour curves and pixel response. If you're really interested in these artifacts, I suggest you research the available modes that the screen supports. I also call upon reviewers to test these modes before commenting on problems.
The response times are always cherry picked from the absolute best circumstances the panel can manage, so you should take it with a grain of salt to begin with. It's all but meaningless.
Take the Syncmaster 2493HM, with a stated response time of 5ms. You might think it can update the screen 200 times completely each second with a figure like that, but no: Here's an image of its ghosting.
The monitor takes input at 60hz, so it has 16.66ms to update the panel completely each cycle. Obviously it can't do that since you can see two images clearly, which means it takes at least 33.33ms to update.
You're now thinking, "Can you even notice it though?" I have the monitor, and yes you can. It's plainly visible sometimes. The most noticable thing is when you have scrolling high-contrast elements on the screen, such as in a game.
The reason for input lag is that manufacturers want the on-screen image to quickly change without ghosting. Here, quickly means "in as few ms as possible", not "without delay". So if you see a change only two seconds later, but the change is instantaneous, that's considered good.
To achieve this, the display electronics must know what the next frames look like. So they buffer two or three frames, then adapt the overdrive on a per-pixel basis to the contents of the next few frames.
Pro: smoother video playing
Con: a delay of two or three frames
Rotaluclac
So, the individual pixels of the panel have a transition from b->w or w->b of x milliseconds, but the sum of those pixels (e.g. the entire screen image) has a transition time of x*5?
Err?
It seems to me that the screen processing takes a fixed amount of time (~50ms), then that processing tells the pixels to change, which takes (~5ms)... Thus the total response is 55. Does the fact that they're overdriving the pixels to get their response time down affect the screen processing? This seems to be the assertion of the article but it doesn't make much sense to me.
None of the online review sites ever mention input lag and on some monitors, it's a huge problem. Three years ago I bought a Dell 2405FPW based on excellent reviews from a number of sites. The monitor lagged badly and as I was using it, more issues became apparent (incendiary backlight, bad viewing angles), none of which were mentioned by any of the review sites.
So beware online reviews of monitors. Better look for user reviews.
Overdrive is commonly used on all types of panels - TN, *VA, *IPS.
It isn't related to input lag as much as the summary would like you to believe. Somewhat, yes, but not that much; also, PVA panels are generally the ones with biggest input lag.
Some *VA panels have an input lag of 3-4 frames, some have only 1; some TN panels have a lag of 1 frame, some have 3. Some panels have overdrive that you cannot even notice, some - like the Dell 2407WHP-HC - will make you want to poke your eyes out.
What's much worse than input lag and ghosting are the eternal marketing races for MOAR BRIGHTNESS!!!11 and MOAR GAMUT!!1ONE, eventually leaving you with a monitor with a *minimum* brightness of 250 cd/m2, happily roasting your eyes out in anything but daylight, and with a gamut so large that skin tones heavily shift towards red, wildly inaccurate colours, and easily-visible fringing when you turn ClearType on (surprisingly, Windows Se7en will have proper low-level wide gamut management and will tone it down to sRGB on request, eliminating all issues; probably one of the few things that are actually good enough in that OS).
When it comes to monitors, HardForum is generally the place you want to thoroughly check out: http://www.hardforum.com/forumdisplay.php?f=78
This is one of the reasons why I refuse to buy LCDs for gaming, both on my desktop and for consoles. Other factors include refresh rates, variable resolution, and numerous quality problems (dead or stuck pixels, color reproduction, viewing angle, brightness uniformity, etc).
Given a choice, nobody would prefer to play on a laggy ISP, so it's really awful that manufacturers don't inform about multiple-frame image processing delays on 60hz monitors.
CRT technology is so mature and LCD so comparatively half baked that I'm totally revolted by the general consensus to throw out completely superior performance in favor of smaller form factor (it's not like they're moved often).
I spent months last year looking for a flat panel to buy that I would want to game on, and came up empty handed, so I simply abstain.
I'm currently using a ViewSonic P220f from a friend after my 8 year old Sony GDM f500r was recently retired, both 21". My consoles are on a 34" Sony WEGA KV-34HS510.
When my tubes finally give out in a few years, I'll be looking for something far better than LCDs to replace them with.
If you aren't a serious game or video editor this probably doesn't matter. I recently bought a new LCD for a dirt low price. Some of its specs are unbelievable (possibly with good reason) like the 15,000 to 1 contrast ratio. It claims a 5ms response time. I haven't tested it like CNET would, but I have seen no problems and am very happy with it.
Think Deeply.
you may want to test drive very carefully any display boasting low integer millisecond pixel response times
So what you're saying is, stick with the low non-integer millisecond response times...?
https://www.eff.org/https-everywhere
In case I'm not the only one who immediately wondered what the latency on their display was.
DigitalVersus Monitor Duels
Ugh, input lagging. To me, this would be an even worse issue than blurring or flicker. Lagging (at least above 30ms) means a 'soupy' cursor, and an end to games which require quick reactions.
I hope this becomes another stat to put on advertising. It's very hard to see unless you hook up a computer and do some testing, so joe public won't care... :(
It's exactly this kind of thing which will make OLED technology win in the end. All the problems associated with LCD (response time, blurring, lagging, contrast levels) will be gone in an instant.
Why OpalCalc is the best Windows calc
You need a monitor with a TnA panel.
Why, without your clothes, you're naked, Miss Dudley!
i know, the solution sound old-fashioned but it should work,,,
The reported problems are not related to "overdrive". What happens is that apparently some screens take the input, store it for 2-3 frames, possibly processing it, and then displaying it. This of course totally anhilates the improvement from 16ms (1 frame) to 5ms (0.33 frames).
So the problem lies in how "response time" is measured. It should be measured as: At t=0, the computer changes the screen from white to black, at what point in time does the screen reach "black". This is not entirely easy to measure, because the starting point is hard to capture, because it is an electronic signal inside the computer, that you have to compare to the light values from the screen. And the data is transferred to the screen at 60 frames per second. So if your sensor is watching the top left, the change in the computer may happen at the time the "beam" was on the middle of the screen. This would result in about 8ms of extra lag.
Buying anything with an LCD display has been a pain in the arse for about twenty years now... haven't you developed a callus back there yet?
You might think, after more than twenty years on the market and continual development and tweaking, that shortcomings like dead/stuck pixels would have been eliminated outright, but here we are still griping about them. How can this BE, when technology is supposed to solve all?
The decline in CRT in favor of LCD has a number of problems. The issues that effect me are true refresh rates and input lag. When you need a stereo display (shutter glasses), accurate and clean switches between frames are required. The current batch of LCD doesn't seem to be able to deliver this (at least without a lot of research).
For years I had a beautiful 24" Sony GDM-FW900, and then it busted. I wish I had known about input lag before I plopped down $600 for a Dell 2408WFP. This thing SUCKS!
1. You seem to assume that there actually is some kind of pro gamer gear. All the pro LCDs are actually as in graphics artist pro, and usually actually have the slowest response times of them all. It's "pro" as in "it'll look like that when printed too" (and maybe we'll throw calibration hardware and software in too, 10bit per colour component instead of 8 if it's a several thousand dollar model, led backlight, etc), not as in "it'll display the image in 1ms". It's mostly static images that'll get displayed on those.
The very panel that goes into one already works against you. The fastest ones are TN+Film, but those tend to be in 6 bit per component and dithering instead of 8, have shitty viewing angles (often to the extent that you can see a slight difference between the centre and the corners just because the line from the pixel to your eye falls differently), and at least according to behardware.com the "+Film" part creates more non-homogenity too. The most accurate ones are VA ones (as in, MVA or PVA), but those are also the slowest by far. Guess which goes into a "pro" level display for graphics professionals? Right.
2. If you have that fast reflexes and actually live or die by shooting 1ms earlier, most TFT's have an extra problem: most first buffer the whole image, then scale/display it, because it's the easiest way to deal with scaling an image of a different resolution. Unfortunately they do it even when you use their native resolution.
I.e., what you see on the screen is actually what they received 1 to 3 frames in the past. At, say, 60 fps, on some models you can actualy see the image as it was received 50ms ago. I.e., the difference between 1ms and 5ms latency of the panel is entirely the wrong bottleneck to optimize there.
(Since you mentioned Fatal1ty, last I've heard he used a CRT, btw.)
Better models in this aspect are starting to appear, but it took a while and they're still few and far in between. Mostly because it's not one of the numbers dangled in front of the fashion victims, so there was very little incentive to do anything at all about it.
3. The numbers you get told are by and large... well, not lies, but the standard was written by the vendors for their benefit not yours. E.g., a 5ms display if it's measured black-to-white-to-black can be actually faster than a 1ms grey-to-grey with massive overdrive, and produce less ghosting.
The short and skinny was that the black-to-white-to-black standard was already a lie by itself, and only used because it was the smallest number you can measure without overdrive. The standard as defined by the vendors lets them ignore the first and last 10% of the moving from colour A to colour B. Even that ought to give you cause for thought: that number didn't say "it will reach colour B in time X" but merely "it will get within 10% of colour B within time X". A 10% error is piss-poor on the logarithmic scale of the eye. And it lets them ignore the long asymptotic rest of the curve. But in a transition from black to white or back they can ignore more of the long tail than in a grey to grey transition, according to their own bogus standard, so that's why everyone quoted that.
This all changed when someone invented overdrive. The idea here basically is that you can accelerate faster and overshoot the finishing line if you want to. The measured time still is "in how much time you can get within 10% of the finishing line." It doesn't matter that then you overshoot by 50% and spend even more time coming back asymptotically from the _other_ side. But you can't do much overdrive o
A polar bear is a cartesian bear after a coordinate transform.
All the good gamers still use CRT displays anyway. Yet another good reason why you still should not switch to LCD.
I may have bitten the bullet and switched to LCD for convienience but it's still a disadvantage for extremely high end video gamers in competition.
If you go to a proper starcraft tournament or a CS tourney the 'pros' are still using CRT's
Here's an example of input lag and this is LCD vs LCD - so there's even some lag on the left display
http://www.newswheel.com/files/IMGP2146.jpg
Interestingly I was playing quake live the other day with some people and one particular guy (who I will admit was bloody good) killed me at least 2 or 3 times whilst running around a corner, I was dead before I could even see him.
We both had the same ISP and ping and I asked what display he used and he still had a CRT.
(He would've beaten me anyhow but none the less it definitely cost me a few lives)
Low double millsecond displays are ok?
http://en.wikipedia.org/wiki/CD#Main_physical_parameters
Scanning velocity: 1.2-1.4 m/s (constant linear velocity) - equivalent to approximately 500 rpm at the inside of the disc, and approximately 200 rpm at the outside edge. (A disc played from beginning to end slows down during playback.)
Others vary a lot, you see everything from CLV (although getting a CLV with good seek times is expensive), CAV, and zoned CAV ánd CLV. Since unlike in the case of audio-CD's there is no real-time requirement, the drive manufacturer is pretty much free to choose whatever they think will result in the product that generates the most profit.
If you watched any video, was there any noticeable mismatch between the audio and the video? Like the movie was dubbed?
It's not just perception or resolution. On behardware.com they actually put them next to a CRT, both are showing the output of the same GPU, and film them with a very high speed camera. You can see that on most TFTs an enemy is already in the middle of a corridor shooting at you, while on the TFT sometimes he's not even on the screen yet.
So, no, its not just bull. The review you read was just retarded, and apparently too eager to rationalize with bullshit instead of actually measuring.
A polar bear is a cartesian bear after a coordinate transform.
My lcd monitor takes approximately 7+ minutes to start up after pressing the power button on my PC!
The monitor's light just flashes on and off forever until you hear some strange long wooosh sound coming from its speakers then suddenly it decides to wake up.
It's ok if it's only been off for some minutes but any longer and I have to go through that annoying sequence again.
It's a Medion S14 monitor (Just to slate them) and it used to be so perfect and responsive.
Oh well :'(
Quite a while ago (2005) I noticed a clear difference in my reaction time playing on a notebook display and playing on my big screen, a Dell 2001FP. I haven't heard something about LCD lag at this time. So I tried to investigate this and found a lag of about 17..20ms for that monitor. Some do lough about people complaining about the lag, but all too often it decides about life and death in FPS games. If you suddendly encounter an opponent the one with the faster reaction time will make the frag. I created two programs to measure the lag of monitors. One is a stop watch application that writes the current time on screen but syncronously with the screen refresh (vertical sync). http://www.draebenstedt.de/reaction/timecode.zip The time is written on screen from top down on a differnt location on screen each time to avoid blurred numbers that are continously overwritten. The second application can measure the lag by tracking a moving pattern with an optical mouse! Don't lough! It works! Please have a look: http://www.draebenstedt.de/reaction/loopback.html
OK, the movie is originally shot at 24 fps.
In the theater, the movie is projected at 48 fps, showing each frame twice, because 24 is too flickery. This preserves the original running time of the movie.
On an NTSC TV, the movie is shown with "2:3 pulldown", which turns 4 film frames into 5 interlaced TV frames (10 fields) by showing the first frame for 2 fields, the second for 3 fields, and so on. So for movie frames [1] [2] [3] [4], you end up with TV frames [1A 1B] [2A 2B] [2A 3B] [3A 4B] [4A 4B]. This preserves the original running time of the movie(*), but can look a little jerky.
On a PAL TV, the movie is shown with "2:2 pulldown", which turns each film frame into a single TV frame (2 fields). Since PAL is 50 Hz, this means the movie is actually shown at 25 fps, so the running time is shorter than the original (a 120 minute movie ends up being about 115 minutes), but it won't be jerky.
On a computer monitor, you can play back the movie at its original frame rate and let the video card sort it out, since the speed at which the media player pushes frames to the card is independent of the speed at which the card sends the frame buffer to the monitor. Depending on your monitor's refresh rate, this may or may not introduce jerkiness (as the GP mentioned, 24 divides evenly into 120 but not 60) or tearing (if you don't wait for vsync).
(* Almost. NTSC has a goofy fractional frame rate, so the movie ends up playing at 23.976 fps rather than 24. The time difference only adds up to a few seconds over the length of a 2 hour movie, though.)
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