Input Lag and Response Times
We've heard frequent complaints about input lag on various LCDs, particularly after our last review of the Samsung 245T. We decided it was time to take a closer look at the subject and see if we could come up with a repeatable test. We ended up settling on a test similar to what we were using to show response times, with a few changes.
We run the Wings of Fury benchmark in 3DMark03, with the resolution set to the native LCDs resolution -- in this case 1920x1200. Our test system is an overclocked quad-core Q6600 (3.30 GHz) running two Radeon HD 3870 cards in CrossFire on a Gigabyte GA-X38-DQ6 motherboard. (This is the same system used in our initial testing of 3DMark vantage.) We connect the test LCD and a reference LCD to two outputs from the Radeon 3870 and set the monitors to run in clone mode.
The reference Monitor is an HP LP3065, which we have found to be one of the best LCDs we currently possess in terms of not having input lag. (The lack of a built-in scaler probably has something to do with this.) [Ed: Before you ask, no, I do not have any CRTs around that I can use as a reference monitor, and frankly I don't want any. They're huge, heavy, and require more power, and the best ones were made over five years ago. Sorry - LCDs are where everything is heading. R.I.P. CRT.]
While the benchmark is looping, we snap a bunch of pictures of the two LCDs sitting side-by-side. We set our camera to f/2.2, ISO-400, and a 1/400 sec exposure in order to get a clear snapshot of the on screen action. (Note that these settings have changed from previous articles.) 3DMark03 lists a runtime with a resolution of 10 ms at the bottom of the display, and we can use this to estimate whether a particular LCD has more or less input lag in our reference LCD. We then sort through the images and discard any where the times shown on the LCDs are not clearly legible, until we are left with 10 images for each test LCD. We record the difference in time relative to the HP LP3065 and average the 10 results to come up with an estimated input lag value.
It's important to note that this is merely an estimate -- whatever the reference Monitor happens to be, there are some inherent limitations. For one, LCDs only refresh their display 60 times per second, so any measurement less than approximately 17 ms is not 100% accurate. Second, the two LCDs can have mismatched vertical synchronization, so it's entirely possible to end up with a one frame difference on the time readout purely because of this. That's why we average the results of 10 images, and we are confident that our test procedure can at least show when there is a consistent input lag/internal processing delay.
Here is a summary of our results, followed by a sample image chosen to highlight the pixel response time of the LCDs. Despite what the manufacturers might advertise as their average response time, we found most of the LCDs were equal in this area -- they all show roughly a one frame "lag", which equates to a response time of around 16 ms.
| Display Input/Processing Lag vs. HP LP3065 | |||||||||||
| One | Two | Three | Four | Five | Six | Seven | Eight | Nine | Ten | Average (ms) | |
| ASUS MK241H | 10 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 |
| Dell 2407WFP | 10 | 20 | 30 | 20 | 10 | 10 | 30 | 30 | 10 | 20 | 19 |
| Dell 2408WFP | 30 | 40 | 40 | 40 | 30 | 30 | 40 | 30 | 50 | 50 | 38 |
| Gateway FHD2400 | -10 | -10 | 0 | 10 | 10 | 10 | 0 | 10 | 10 | 0 | 3 |
| Gateway FPD2485W | 30 | 10 | 20 | 20 | 20 | 10 | 0 | 30 | 20 | 20 | 18 |
| HP w2408 | 10 | 10 | 0 | 0 | 0 | 0 | 0 | 10 | 0 | 0 | 3 |
| LaCie 324 | 40 | 30 | 40 | 30 | 40 | 50 | 40 | 50 | 50 | 30 | 40 |
| Samsung 245T | 30 | 30 | 30 | 30 | 30 | 20 | 30 | 30 | 20 | 20 | 27 |
| Samsung 2493HM | 0 | 10 | 0 | 0 | 0 | 10 | 0 | -10 | 0 | 10 | 2 |
 ASUS MK241H |
 Dell 2407WFP |
 Dell 2408WFP |
 Gateway FHD2400 |
 Gateway FPD2485W |
 HP w2408 |
 LaCie 324 |
 Samsung 245T |
 Samsung 2493HM |
The table tells a clear story: all of the S-PVA panels as we mentioned clearly have more input lag/internal processing lag than all of the TN panels. This is a pretty shocking result, as it indicates that the problem may actually be inherent in S-PVA technology, although there are still panels that do better in this area. The Gateway FPD2485W and Dell 2407WFP both have an input lag just under 20 ms -- or a one frame delay on average. The Samsung 245T has a 27 ms delay on average, indicating it would be one or two frames behind what is actually happening. Worst of all are the Dell 2408WFP in the LaCie 324, which have a two or three frame lag. (This is discounting any other lag that is present between the user and what they are seeing on the display; there's also a slight amount of lag associated with reading input from your mouse/keyboard, processing that input, rendering the resulting image, and sending that to your display.) In contrast, the four 24" TN panel LCDs all more or less match the HP LP3065.
Thus, we have no choice but to conclude that if you are seriously concerned about input lag, you will have to sacrifice viewing angles, color accuracy, and/or overall display quality in order to avoid this on the current 24" offerings. On the other hand, we have played games on all of the test LCDs, and we honestly can't say that we noticed any difference in our overall performance. But we weren't hopped up on Bawls and we don't have a 1337 name like Fatal1ty. Competitive gamers will probably feel differently.
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Rasterman - Friday, May 2, 2008 - link
I wish you would have reviewed an old CRT to compare the LCDs to. I still have my 22" beast and would upgrade if I knew if an LCD could beat its image quality. Comparing the best LCD to the best CRTs of 5 years ago would be interesting as I'm sure a lot people are still holding on to theirs given the results of the Valve survey suggesting more than 70% of gamers are using CRTs.JarredWalton - Friday, May 2, 2008 - link
The simple fact that new *quality* CRTs are not being made can't be overlooked. Five years back, you could get a high-end 22" CRT that would do 2048x1536 @ 85Hz (or 1600x1200 @ 110Hz). Now, most 21" CRTs only manage 1600x1200 @ 75Hz. Then throw in all the crap you have to deal with in terms of image centering and pincushion and trapezoidal distortion - all things that are completely non-existent on LCDs.When you consider size, weight, and cost, I'll take LCDs every time. OLED or some other display technology may replace LCDs, but conventional CRTs are brain-dead and the manufacturers are getting ready to remove life support.
Rasterman - Tuesday, May 6, 2008 - link
I totally agree it makes no sense to buy a new CRT, but what I am asking is if its worth it to UPGRADE based purely on image quality. This is why I suggested comparing it to a CRT of 3-5 years ago and not a new one. Weight, size, and taking 10 seconds to align the image are all secondary to image quality. I don't see how you can ignore the fact that most people buying high-end LCDs are upgrading from high-end CRTs.JarredWalton - Tuesday, May 6, 2008 - link
I (and many others) upgraded from CRTs about three years ago. I have never regretted the decision. I think colors are better, I love not dealing with image distortion (i.e. pincushion, trapezoidal, rotational, etc. adjustments), the size reduction at the same time as you get a larger screen area (22" CRTs are the equivalent of 20" LCDs).... I could go on.I think most professionals upgraded to LCDs a long time ago; the people who remain with CRTs are those who are ultra-dedicated to high refresh rates and faster pixel response times. The only area where that really matters is gaming. Throw in the fact that the phosphor used on CRTs starts to fade after 4-5 years, and even if you have the best CRT ever produced it's probably time to upgrade.
In short, I am not ignoring CRTs; I am simply refusing to beat a dead horse.
probert - Friday, June 13, 2008 - link
This may be an old thread but I'd like to put in my 2 cents.Love your reviews but I think you're wrong about CRT's. They're used more than you think and for someone who does print work they are an excellent inexpensive alternative to a really good lcd.
For example Pixar has stockpiled CRT's (trinitron FD tubes) and I suspect a lot of places do. It takes about 15 minutes to calibrate one and - as far as being bulky - I'll admit I won't take mine backpacking any time soon, but why would I want to.
There are sites that still sell new and refurbed CRTs with the trinitron FD tubes (Generally Dells and IBMs). These are superb and cost about $200.
They are great for print work You can adjust not just rgb but bias and gain on each channel. Their color accuracy and ability to render gradients may be matched by a top line NEC - but at 1/6 the price.
My set up is a 21" crt and an 8bit lcd for web work and checking sharpening. (In fact, I don't calibrate the LCD presently to simulate the general web experience. This is driving me a little crazy and I may tighten it up.) The whole rig cost $400.00 - has plenty of real-estate and has very good monitor to printer accuracy.
I'm happy that people who don't need this precision use LCDs, as it saves energy and materials, but the crt is a very viable alternative for someone who does need accurate color and good tonal range for short money.
In fact, I'll toss the gauntlet and say that for this particular niche - they are better than, or, as good as, any LCD on this or any other planet.
icthy - Friday, May 2, 2008 - link
Just curious, has anyone actively considered buying either two 24" monitors as a substitute for one 30" monitor (or the other way around). I know it depends what one does, but I'm so frustrated working on my one 20" monitor, I want to go big, big, big! But I'm unsure if the cost of the 30" is worth it.JarredWalton - Friday, May 2, 2008 - link
I personally prefer one large LCD over two smaller LCDs. Working on large images in Photoshop, I can use all the resolution I can get. Splitting an image over two displays just isn't the same to me. That said, I know others that really like having two 24" LCDs. My dad is set up that way, so he can have web pages, documents, etc. on one side and spreadsheets, other web pages, and such on the other. In fact, my dad sometimes has both 24" LCDs in portrait mode, so he can have a virtual resolution of 2400x1920 and see long segments of text that way.Total cost of two 24" LCDs would be $900 to $1200 depending on brand (or $1800+ for two LaCie 324 LCDs). A single 30" would run at least $1000 I think (outside of used/refurbs), and some like the 3008WFP would cost as much as $2000. Total screen resolution and area is higher for two 24" LCDs: 12.5% more pixels and 28% more screen area. If you can live with the black back between the LCDs, two 24" LCDs is a more economical/flexible approach overall.
icthy - Saturday, May 3, 2008 - link
Thanks. I'm tempted by the shear prettiness of one 30" monitor. But I tend to run Linux, and than use windows under Vmware. I suppose with two 24" monitors, I could have one Vmware-Windows display, and one for my Linux-computational stuff--although I don't know if the vmware drivers would support that.KLC - Friday, May 2, 2008 - link
Your review confirms my experience with the Dell 2408, it is a great monitor and also an excellent value for its performance. Just look at comparably sized NECs and LaCies to calibrate your value gauges. I got it for $599 with free shipping.I've read the comments about pink tinges and banding and on and on and on in hardware forums, like Jarred I've had no such problems with mine. I mostly use my system for photoshop, video editing, office apps and websurfing, no games so lag time doesn't matter to me.
The ergonomics are also outstanding. You can easily adjust height, tilt, etc. And like all Dell monitors I think they've done a great job of industrial design. If you like all of your tech to mimic a Transformer you'll have to look elsewhere, but if you like something elegant and functional Dell has few that surpasss them.
It does put out a lot of heat, it is very bright, too bright, out of the box and I still haven't been able to use my Spyder3 Pro to fix that to my satisfaction. I'm going to use Jarred's RGB settings and see how that goes.
One mildly irritating thing, after playing around with the On Screen Display and the Spyder for several days the white contrast marking on the front panel buttons has completely worn off. Jarred, did you see any of that on your sample?
But I have no buyer's remorse over this purchase, and that is something I don't experience very often.
JarredWalton - Friday, May 2, 2008 - link
I haven't noticed any issues with the button labels wearing off, but then I might not be using them enough, or perhaps your fingertips have more oil than average and that's causing the loss. After the labels are gone, you can pretend to have a Samsung 2493HM and guess at which buttons do what until you get the layout memorized. :)