Response Times and Buffering

A topic that almost always comes up as a problem with LCDs is their slower response times relative to CRTs. There's no doubt that even the best LCDs still exhibit some slight pixel smearing, but the vast majority of users are okay with the level of performance we have available now. Image retention on your retinas also occurs to some extent, so even if you can completely eliminate the smearing effect at the display level you won't necessarily "see" a perfectly crisp transition.

Besides lag at the pixel level, there's also potential for buffering lag within the LCD's image processor before anything is ever sent to the panel for output. This can be particularly noticeable on some HDTVs when connected to a computer, as HDTVs will often do a significant amount of image processing. Whether or not delays are caused by the internal circuitry or by the LCD crystal matrix taking a moment to align itself isn't really important; the end result is what matters, so a display that updates quicker is usually preferred, especially by gamers.

Like the Dell 2407WFP and Gateway FPD2485W LCDs (which also sport S-PVA panels), the 2707WFP advertises 16ms TrTf and 6ms GTG response times. Other LCDs are rated even faster, and ratings aren't always accurate, so let's see how these displays compare in practical use. We use the Dell 2407WFP as our baseline model for all lag/smearing tests; it actually is regarded as being a slightly slower display due to buffering within the panel circuitry, but so far we haven't been able to find any LCDs that are more than one frame faster.

The Dell 2407WFP is on the left in all of the following images. We then started the first game demo from 3DMark03 and took numerous pictures, after which we selected several representing the best and worst case results that we could find. With all of the LCDs running a 60 Hz refresh rate, new frames are sent to the display every 0.017 seconds, so that's our granularity. Pay attention to the value of the Time field in the following screenshots, as that will show whether the two displays are showing the same frame or not. Results for the other displays are available at the following links:

Acer AL2216W #1 Acer AL2216W #2
Dell 2405FPW #1 Dell 2405FPW #2
Dell 3007WFP #1 Dell 3007WFP #2
Gateway FPD2485W #1
HP LP3065 #1 HP LP3065 #2



Click to enlarge

Despite having the same rated response times, the 2707WFP always seems to be the same or slightly behind the 2407WFP on the actual content being shown. There doesn't appear to be any more pixel lag, but the signal processing lag may be adding almost 1 frame to the transition times. Then again, you can clearly see the artifacts from image tearing, particularly in the first image, and you can see that our refresh locations are not identical, so that may account for the differences at the bottom of the display were the time and frame number are located. Too bad we don't have higher refresh rates available on LCD panels (yet).

In practice, we couldn't tell that either display was any faster/better in terms of image smearing. It was only when we resorted to using a camera that we could capture the slight differences between the displays. It's entirely possible that those with more acute eyesight might be able to notice a difference, but we feel that most people won't have a problem with the slight image smearing that occurs on modern LCDs. As we've said in the past, this is something that will vary by individual, so if you are bothered by image smearing be sure try out a display in person to see if it's suitable for your needs.

Viewing Angles and Gradients Uncalibrated Results
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  • JarredWalton - Wednesday, April 4, 2007 - link

    A perfect example of stuff that doesn't look right with a higher DPI setting is anything that uses a bitmap. All of the icons at 120dpi tend to look like crud in XP. There are just far too many areas of Windows and the applications that run on it that are built around pixel sizes, so changing DPI settings only sort of affects them.

    Anyway, the point isn't whether or not higher DPI is good or bad. You like it, others don't. That's the main idea behind that introduction: an explanation of why higher pixel pitch can be a good thing. I really do have poor vision (an irregular astigmatism that can't be corrected without a retina transplant, so I live with slight double vision). I find many of the high DPI screens to be undesirable, although I do like higher resolutions for image work.
  • kalrith - Wednesday, April 4, 2007 - link

    Since we're discussing pixel pitch and poor eyesight, I thought I'd mention that one of my coworkers has such poor vision that he's using a 21" LCD at 800x600 resolution and thinks it's "just right".

    Also, out of the 10 19" LCDs we have, only one person runs hers at the native res. Everyone else uses 1024x768.
  • LoneWolf15 - Thursday, April 5, 2007 - link

    This is one reason why I "downgraded" (the rest of the specs are similar, other than that I also shaved 2 pounds of weight) from a laptop with a 15" 1600x1200 UXGA display to a 14" 1024x768 XGA display. At 15", picture detail was incredible, but text for web browsing was giving me sore eyes and headaches. I wouldn't mind having 1280x1024 at 14" or 15", but since I'm not paying for it, beggars can't be choosers.

    It's also why I returned my Dell 2007WFP and exchanged it for a 2407WFP. Higher resolution, but larger pixel pitch as well.
  • kmmatney - Wednesday, April 4, 2007 - link

    I'm another person who likes big pixels. Work tried to give me a 17" LCD, but I would have none of that. I then tried a 21" Samsung at 1600 x 1200, but it was still too small. Now I have a 20" LCD running native at 1400 x 1050 and its really nice. I have a laptop with small pixels that I use when I travel, but I'm much more productive when I can see everything clearly.

    I would love to have this display, but it really needs to come down in price.
  • strikeback03 - Wednesday, April 4, 2007 - link

    my vision is awful uncorrected - way beyond not being able to see the big "E". But since I'm always wearing glasses or contacts anyway I like high-DPI displays. Love my thinkpad with the SXGA 15" display. The UXGA 15" would probably be hard to read though.

    My boss has a ~20" CRT that he runs at either 800x600 or 1024x768.
  • jc44 - Wednesday, April 4, 2007 - link

    OK - I admit it - I'm stunned. With the exception of your colleague with the poor eyesight I find it hard to conceive how anyone would prefer (presumably) a slightly fuzzy (due to scaling artifacts) 1024x768 to a sharp 1280x1024 on a 19" LCD. I could simply not put enough information on the screen to be able to do my job at that resolution without resorting to a lot of printouts.

    Well horses for courses I guess - thanks

    JC
  • xsilver - Friday, April 6, 2007 - link

    lol - the amount of people that have their lcd monitors set to non native resolutions is insanely funny.
    but even more insanely funny is how many people say they cant see anything wrong with the scaling artifacts and fuzziness.

    I haven't done much (any) testing on this in gaming though - is the distortion just as bad in gaming when running a non native res? getting a 20" lcd or above these days has pretty much required a high end graphics card to be purchased if any gaming wants to be done if you want to run native res.

    still prefer crt atm myself but I realize it will be inevitable that i'll have to make the switch and need to figure out some options.
  • mitchell123 - Thursday, December 3, 2009 - link

    hello Friends
    Thios is a nice article.......for everyone...........
    ==============
    Mitchell
  • Tommyguns - Wednesday, April 4, 2007 - link

    19" Viewsonic lcd here. you guessed it. 1024x768 and it suits me just fine. not that i have bad eyes at age 22 or anything, i just like being able to clearly see everything. I game hard as well and it works out just fine. i do have it in clone mode going to an aux 17inch crt thats about 20 feet away. higher res. is nice, but i prefer big letters, with out the squints sometimes.

    it would be nice to know what is around average in terms of gpu's, to be able to use these larger lcd's. average wasnt always a super highend 8xxx series card.

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