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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.
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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?
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Do plasma displays have this same issue?
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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.
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
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.
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.
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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
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