BenQ E2200HD and E2400HD - 1080P FullHD LCDs
by Jarred Walton on November 4, 2008 5:00 AM EST- Posted in
- Displays
Display Lag and Response Times
We've heard frequent complaints about "input lag" on various LCDs, so that's one area we look at in our LCD reviews. You might be wondering why we put input lag in quotation marks, and the reason is simple: while many people call it "input lag", the reality is that this lag occurs somewhere within the LCD panel circuitry, or perhaps even at the level of the liquid crystals. Where this lag occurs isn't the concern; instead, we just want to measure the duration of the lag. That's why we prefer to call it "processing lag" or simple "display lag".
To test, we run the Wings of Fury benchmark in 3DMark03, with the resolution set to the native LCD resolution -- in this case 1920x1080. Our test system is a quad-core Q6600 running a Radeon HD 3870 on a Gigabyte GA-X38-DQ6 motherboard -- we had to disable CrossFire support in order to output the content to both displays. 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 display lag. (The lack of a built-in scaler probably has something to do with this.) Again, we know some of you would like us to compare performance to a CRT, but that's not something we have around our offices anymore. Instead, we are looking at relative performance, and it's possible that the HP LP3065 has 20ms of lag compared to a good CRT -- or maybe not. Either way, the relative lag is constant, so even if a CRT is faster at updating, we can at least see if an LCD is equal to or better than our reference display.
While the benchmark is looping, we snap a bunch of pictures of the two LCDs sitting side-by-side. 3DMark03 shows the runtime with a resolution of 10ms at the bottom of the display, and we can use this to estimate whether a particular LCD has more or less processing lag than our reference LCD. We 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 processing 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 we cannot specifically measure anything less than approximately 17ms with 100% accuracy. Second, the two LCDs can have mismatched vertical synchronizations, so it's entirely possible to end up with a one frame difference on the time readout 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 lag/internal processing delay.
Despite what the manufacturers might advertise as their average pixel response time, we found most of the LCDs are basically equal in this area -- they all show roughly a one frame "lag", which equates to a response time of around 16ms. In our experience, processing lag is far more of a concern than pixel response times. Here is a summary of our results. Images for the E2200HD and E2400HD can be found on pages four and seven of this review; images for the remaining LCDs are available in our 24" LCD roundup.
| Display Input / Processing Lag vs. HP LP3065 | |||||||||||
| A | B | C | D | E | F | G | H | I | J | Avg. (ms) | |
| ASUS MK241H | 10 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 |
| BenQ E2200HD | 0 | 0 | 0 | 10 | 0 | 0 | 0 | 0 | 0 | 0 | 1 |
| BenQ E2400HD | 0 | 0 | 0 | 10 | -10 | 0 | -10 | 0 | 0 | 10 | 0 |
| 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 |
As mentioned previously, all of the S-PVA panels we have tested to date show a significant amount of input lag, ranging from 20ms up to 40ms. We will have a look at an MVA panel in the near future, which will hopefully show results similar to the TN and S-IPS panels, but for now we can only recommend avoiding S-PVA panels if you're concerned with input lag.
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10e - Tuesday, November 4, 2008 - link
Keep in mind, that if you set 1:1 pixel mapping on your video card whether ATI or nVidia, both of these monitors will display 1:1 with black borders. 1680x1050 works perfectly as do other resolutions. To me this is the only reason you need 1:1 pixel mapping, and if the monitor supports it, it's not a big issue if it is not explicitly stated in the menus.A PS3 is a good benchmark here, and if the monitor was set to 1:1 you would get a full screen XMB/dashboard, and most games, running at 720p would display a tiny image with large black borders elsewhere. This is why proper aspect ratio scaling is important.
Additionally, for the seldomly used 480p resolution, the monitor can simply be set to stretch to full screen so that this content is displayed at proper aspect ratio.
I would say 1:1 pixel mapping in all cases is more useful for 16:10 monitors as opposed to 16:9.
wicko - Tuesday, November 4, 2008 - link
One problem I've had with TN panels is that under certain conditions in a game I've noticed a strange artifacting appear. It is most obvious under Source engine games, like Lost Coast, HL2, CS:S, but also noticeable in other games and even in movies. In the game, to reproduce it all you have to do is look at the sky and move the mouse around at varying speeds, and pay attention to the clouds. I noticed this magenta colouring appear in the silhouette of the cloud in the position it used to be, and then it will quickly disappear. Sometimes its other colours, it depends on whats being displayed. I've noticed this in movies (in the latest Bourne movie with the fight where he pistol whips the guy in the end) and in games. I think it was really bad in Quake 4, the part where you're launched into the air in a pod, and fog is rushing past, you can see a strange discolouring going on. Not sure what this is called, I haven't been able to find any info about this. I've noticed it with 3 different monitors with TN panels (a year or two ago) and since I've bought an LG panel with 5ms response time (not sure which panel) I haven't been able to reproduce it. Can anyone tell me what that artifacting is called, and do these new BenQ monitors have the same issue?JarredWalton - Tuesday, November 4, 2008 - link
It may have simply been an issue where the transitions between colors ended up with some image persistence that looked weird. You can see in the lag/response time images that there's an afterimage on moving objects, which ends up being half way between what was there last frame and what will be there in the next frame. It's likely that in some instances the half way point looks magenta.Some people call this "smearing", others "ghosting", or "motion blur". I call it image persistence I guess.
wicko - Tuesday, November 4, 2008 - link
I think this is a little different. I've seen ghosting before, and I was under the impression that low response time monitors don't have that issue. You only see this situation occur with certain colours, otherwise its completely unnoticeable.JonnyDough - Wednesday, November 5, 2008 - link
Whatever you choose to call it, in my experience 5ms or < = none of it. On 8ms monitors it is still noticeable. My advice when buying a monitor is to shoot for integrated no speakers, HDMI, 1080P, matte finish on the screen and bezel, and at a 2ms response time. Also, anything under 21.5" is a waste of time in my opinion. A 19" or 20" monitor will suit many people just fine. I use Samsung Monitors and I think they're fantastic. I have the 204B and the 215tw, both of which have served me well with only one dead pixel in 4 yrs. I got the 20" for gaming with a 2ms response time, and the 22" (8ms response time) because it has component jacks. The only downsides are that I bought them as HDCP and HDMI were just coming into fruition, and that the 215tw has some worthless speakers which not only contribute to a rise in the cost of the product, but the weight and size of it too.wicko - Wednesday, November 5, 2008 - link
Like i said, I've only seen this occur with 2ms panels. 2 of them were samsung (I can't remember what the models were) and another was the Viewsonic Vx922 (although there was considerably less of that happening to the VX922, a much higher end panel than the samsungs). On the LG, a 5ms panel, I haven't noticed this problem, which leads me to believe that its *not* ghosting. I've seen ghosting before. The whole screen kind of slides around, and its more obvious in darker areas. However, this only happens with certain colors, as far as I could tell, and they were all light colours.MadMan007 - Wednesday, November 5, 2008 - link
The ms ratings of monitors is pretty often bs anyway. The overdrive required to get the fast speeds you mentioned can be done well or poorly, it sounds like the ones that had the problem were done poorly.Gizmonty - Tuesday, November 4, 2008 - link
I bought an E2400HD about a month ago (in Australia) and it came with a DVI cable as well as a VGA cable. I've been very happy with it.Slash3 - Tuesday, November 4, 2008 - link
Regarding the lack of 1:1 mapping, it can still come in quite handy for people who sometimes play older games, which commonly supported resolutions no higher than 1280x1024. With 1:1 mapping, this would result in a very close vertical fit, as intended (albeit with the unavoidable black bars on the left and right). Having to stretch the image to what amounts to 28 pixels in each direction (up and down) will result in reduced image quality with no perceived gain in size. This won't affect all users, but it is certainly a feature which separates the quality displays from the budget models.For 1280x720 content, scaling to fit is the obvious solution, as the aspect ratio is unchanged. That said, it's always nice to have the option. Sometimes, the pixels should only go where they're intended to be.
JarredWalton - Tuesday, November 4, 2008 - link
Agreed... which is why I list it, but at the same time it's not quite as critical as getting the AR correct with stretching (at least if the user asks for it). 1:1 is just a nice extra, which is becoming less necessary as time goes by. If it's there, though, bonus points. :)