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."

Comments

Another thing to look out for

[Hyppy]

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.

Re:Another thing to look out for

[Elledan]

6-bit TN panels don't seem like such a good idea to me, as the interpolation (rapid cycling of pixels to get the desired colour) used to compensate for the lack of full 16.7 million colours other screens have is (together with the flickering of CCFL backlights) responsible for most of the complaints about LCD screens giving people a headache.

As for the article topic, any screen with an input lag of >1 ms will never be 'good' at displaying rapidly changing images, and will be nearly worthless for rapidly-paced games. Plasma, CRT, SED, FED, OLED... all technologies with sub-1 ms latency. Getting that 15" OLED screen LG will be releasing this year as a monitor may not be such a bad idea. Sure, it's not as big as your 24" LCD, but it will have perfect colours and blacks, extremely low-latency, low power-usage, weigh even less than an LCD, and so on.

Let's admit it, LCDs were just an intermediate technology for displays as margins in the CRT market got lower and lower, while new display technologies which could match or beat CRTs in IQ and other factors were still a while off.

Re:Another thing to look out for

[Amouth]

"but the whole 6/7/8 bit and response time thing: is it noticeable?"

yes - it is.. I remember when gateway first started putting out LCD's my boss got me one.. i tried using it for about 3 days before i put my old CRT right back.. the ghosting was so bad - now modern panels don't have that much of an issue BUT the color depth is an issue..

right now i run dual screens at work.. a nice Samsung via DVI and the laptop screen as the primary.

the Samsung is wonderful - even true colors.. where as the laptop (thanks dell) is horrid and you can see artifacts on gradients because it just doesn't have the color depth.. it also has very poor contrast so if i have it in the car or out side in day light by the time i turn the brightness up to read it it is all washed out.

to the Home user.. yea it doesn't matter really - but to someone who spends 8-14 hours infront of the screen it matters alot.. if there was a way to replace the pannle in my laptop with a better one i would do it in a heart beat.

Re:Another thing to look out for

[Mprx]

Consider a mutual surprise situation where both players react with identical 180ms reaction times. One has hardware with total latency of 30ms, while the other's hardware chain has total latency of 40ms. The latter player probably thought that extra 10ms latency wasn't worth worrying about, but here it is responsible for his loss.

As for motion quality, 60fps is clearly inadequate, but in my experience there are greatly diminishing returns beyond about 100fps. Note that this is on a CRT with an impulse response characteristic, on sample and hold displays a higher frame rate will be needed to compensate for the temporal smearing. In the opinion of some experienced FPS gamers, a true 120Hz LCD comes very close to a CRT:
http://www.hardforum.com/showthread.php?t=1387713

Re:Another thing to look out for

[Endo13]

Yes you won't notice a lag improvement at less than 5MS, nor should you. However, the other component that is often overlooked in this (and I used to as well, until a friend demonstrated the difference to me at a store after I tried to tell him he was wrong...) is the refresh rate. Any more, with most LCDs at a 5MS or less response time, it's the refresh rate that is now causing movement lag on the screen. It's much less noticeable on a small monitor though (and by "small" I'm including basically an screen that's small enough to be just a monitor and not a TV) than it is on a larger TV. But don't just take my word for it - go to your local big electronics store and see for yourself. Find a screen with a 120Hz refresh rate and one with a 60Hz refresh rate next to each other. Watch for scenes with movement in them. You'll quickly see the difference. The 120Hz looks smooth as silk, while the 60Hz looks painfully choppy in comparison. Of course, the problem is there's very few actual LCD monitors (if any) that offer a high enough refresh rate to deal with this issue.

Re:Another thing to look out for

[Anonymous Coward]

Re: ShadowRangerRIT,

that is actually a lie. Professor Michi Okaku has done some rather interesting experiments into the human perception of time. Results suggest that at moments of extreme risk to life (or more simply, VERY EXCITING times), ones brain activity speeds up, and conversely their perception of time actually slows down.

In the videos, one of the best experiments his team came up with was tuning a LED display to mask a two digit number in a flicker rate "faster than a human eye" can detect, and having the subjects bungie jump and try to read the hidden number while falling.

Suffice to say the results are pretty impressive.

Re:Another thing to look out for

[slyn]

I don't know about that, when playing Rock Band adjusting the Video or Audio lag as little as 2 ms can have a dramatic effect on my scores or note streaks, or on the harder songs whether I pass in the first place.

For example, on this song on expert, adjusting from a 6 ms video lag to a 4 ms video lag ment the difference between passing only by cheesing my way through the song and passing badly with strained arms (i'm not a real life drummer, and the song is faster paced that it seems on video so it dominates me endurance-wise).

Games like Rock Band and Guitar Hero are a little different in that you are reacting to things that you know are coming and can anticipate, but that doesn't change the fact that I can "feel" the difference between a perfectly tuned HD lag and one only 2 ms off, as well as differentiate whether the delay is to short or to long respectively.

Re:Another thing to look out for

[Mprx]

Vi and vim are both poor text editors in that they trick you into thinking you are highly productive because most of your time is spent on intense thought. This is subjectively quick, but usually measures slower than simpler interfaces. When hardware was the bottleneck spending a lot of time in thought to avoid waiting on hardware might have improved productivity, but now we have displays that update faster than 5fps it is counterproductive.

Re:Another thing to look out for

[hairyfeet]

That is why if you care about such things, and don't have a teeny tiny desk, you should go talk to the local PC shop about a CRT. I picked my CRT for $45, has a great picture and plays my FPS games with a nice clean screen. I have him keeping an eye out for a couple of 19-21 inchers so I can sock a few back. Hell he gets them cheap enough I don't even bother keeping monitors in my shop anymore for anything but displays and instead just send them to him if they need a monitor. I have found in just about every town there is a little mom & pop shop that can score you great deals on monitors.

So why go through all the hassle if you game when you can just pick up a monitor from the local shop and keep the cash flowing locally? I know that he is happy for the extra business I send him and I am happy with my nice CRT. And if you are playing games on a PC I doubt it is going to be a low power "green" PC anyway so why risk spending the cash on something that'll give you problems? I don't get as much time to play as I'd like so when I do get a chance I want everything to be nice and pretty. And my old faithful CRT does perfectly, whether blowing up the splicers in Bioshock or slaughtering the good guys in BFME 1&2. So if you are having problems with your LCD like in TFA, why not go to the local shop and see what they got in stock? Sure as hell beats having one of those heavy bastards shipped across country that's for sure.

Re:Another thing to look out for

[pipingguy]

I read this today, and although it's not related to monitors it's at least somewhat relevant to graphics performance. NavisWorks is a CAD-type visualization program used in engineering and architecture to provide live fly-throughs (and other cool stuff) inside 3D models. Workstation cards cost about $800, while consumer-level cards cost about $150.

There are two types of graphics cards commercially available: workstation and consumer. Workstation graphics cards are much higher priced than consumer cards, because they generally offer more stable drivers and are tested and optimized to work across a wide range of leading CAD applications. Examples of current workstation quality graphics cards include NVIDIA Quadro® FX and ATI FireGL(TM).

Consumer graphics cards are usually relatively inexpensive. However, they are generally optimized for video games, and it is necessary that you install the latest driver versions as they are released. Examples of current consumer quality graphics cards include NVIDIA GeForce® FX and ATI Radeon(TM).

Autodesk performance testing has found that NavisWorks performs well on both workstation and consumer graphics cards, with neither offering any performance advantage over the other. It is strongly recommended that you buy the best card your budget can afford and keep the drivers up to date.

Source: http://usa.autodesk.com/adsk/servlet/ps/item?siteID=123112&id=11905783&linkID=10382101

Re:Another thing to look out for

[slyn]

No, I'm not claiming that I'm perfect, I never even claimed I could do what your saying.

What the article is about is various forms of lag inherent to certain types of monitors. Someone claimed that any lag at around 10 ms or less will have no effect on gameplay. That is false. When playing a game like Rock Band the timing window in which a note is open to be hit is probably around 40 ms, maybe a little less, maybe a little more. If your Video Lag as calibrated by Rock Band to offset the inherent lag of the TV is off my 2 ms, then you effectively handicap yourself out of 2 ms. Now 2 ms is not much in the grand scheme of things, but relative to the 40 ms window that I can hit the note in the first place, it is a loss of 5% of the perceived available time to hit the note.

BECAUSE I'M NOT PERFECT AND ALL MY STRIKES VARY IN ACCURACY, that 5% loss could mean the difference between an 100% full combo or a -1 note 99%. The difference will become especially striking when I'm playing a 2k+ note song or if I'm playing a song that is extremely fast paced like the one I used in the example.

The reality is not that I'm actually consciously noticing the video lag, but that through the interaction with the game I can tell if there is a lag of >10 ms. I threw out the 2 ms example because I recently changed the video lag and it made a big difference on a song that I have been struggling with.

And I'm not claiming I'm the only one who will notice an improvement from this. I have a friend who used to play only on hard and had a notable improvement in how well he played after I helped calibrate his TV for him. It took a couple tries to get the right delay, but once it was configured he began to ace songs relative to how he was playing them before, and his video lag was only changed from 0 to 6 ms IIRC.

Review display's MODES

[MessyBlob]

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.

Reason for input lag

[Rotaluclac]

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

Online reviews sites and LCD reviews

[dusanv]

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.

Re:I'm a CRT holdout (rant)

[toddestan]

Actually, I don't know if I would say LCD technology is mature yet. LCD technology really hasn't done much in the past few years except get cheaper. In some ways it's moving backwards, with new problems like input lag cropping up in the pursuit of meaningless marketing numbers. You could argue days of the best LCD panels are behind us - you can't even get a decent quality LCD anymore in any new laptop (they are all TN-based), and the most amazing LCD ever made (the IBM T221) was discontinued several years ago with nothing to replace it. You would think that the Sony LCD I bought, like you, about 5 years ago would be an antique by now, but sadly with its IPS panel, it's probably better than anything being sold in Best Buy right now.