Let's Talk Panel Technologies

We've already given a brief rundown of TN panels and what they offer, but let's expand that to include the other three panel technologies. Here's the breakdown:

LCD Panel Technology Comparison
Panel Type IPS MVA PVA TN
Viewing Angles Excellent Excellent Excellent Okay Horizontal; Poor Vertical
Color Quality Usually Excellent Good to Very Good Usually Excellent Usually Good
Contrast Ratio >500:1 >500:1 >500:1 Usually >500:1
Color Gamut Depends on Backlight Depends on Backlight Depends on Backlight Depends on Backlight
Processing Lag 0ms (Usually?) 0-3ms 17-50ms 0-2ms
Response Time 6ms GTG 6ms GTG 6ms GTG Typically 2ms GTG
Cost Very High Very High? High to Very High Low to Medium

There are many similarities between IPS, MVA, and PVA - and note that these are now usually "Super" IPS/PVA or "Advanced" MVA. There are a few variants within the base panel type (i.e. E-IPS, H-IPS, and S-IPS), but the patterns generally remain true. Even TN panels have several areas that often overlap with the other techs. Let's look at the various areas in detail.

Starting with contrast ratios and color gamuts, modern LCDs have now reached the point where all panels will generally achieve a greater than 500:1 contrast ratio. Do not confuse this with "dynamic" contrast ratios, where the backlight can vary in intensity to help produce darker blacks and brighter whites at the cost of color accuracy - and it's also impossible to have bright whites and dark blacks concurrently, unless you have zoned backlighting, as current panels run the backlight at a uniform level for the entire display. Backlights also affect color gamut, with the key aspect being how much of the standard color spectrum the backlighting creates. Anything over 100% of Adobe RGB 1998 is overkill, and for most users even 82% of Adobe RGB 1998 (100% NTSC) is sufficient.

The other areas show more differentiation. Viewing angles greatly favor anything other than TN. It's worth noting that while vertical viewing angles often aren't as important as horizontal angles, if you want a display that can run in portrait mode you will definitely want to avoid TN panels (since in portrait mode the poor vertical viewing angles become horizontal angles). Manufacturers are also very generous in how they determine viewing angles, as they only require the display to maintain a 10:1 contrast ratio to qualify as "viewable". Realistically, we would say TN panels have a vertical viewing range of about 30° (15° up/down) before you notice severe image quality changes (i.e. from above the display becomes washed out, and from below it becomes very dark). Horizontal viewing angles on TN panels are probably closer to 60°, or even 90° if you're not super demanding. Compare that to the claimed 160° vertical/170° horizontal and you'll realize how inflated this spec has become with the target 10:1 contrast ration. In contrast, IPS/MVA/PVA all manage a fairly consistent 120° viewing angle in both vertical and horizontal alignments - possibly more if you don't mind the trapezoidal distortion caused by viewing from oblique angles. These displays advertise 176 or 178° viewing angles.

Color quality is also generally better on everything that's not TN, although here the (only) MVA panel we've tested seems to fall a bit short. When combined with viewing angles and the distortion that can cause to colors on TN panels, we'd stick with one of the other technologies if you want to get accurate color. In truth, this is mostly important for imaging professionals, as your eyes and brain will compensate to the point where you usually won't notice the difference. TN panels can also perform well in color accuracy, but they frequently do not because the manufacturers don't feel that's the target market - and in fact many displays have poor color accuracy by default because a lot of people prefer saturated colors. Also note that TN panels do not natively reproduce 8-bit color spectrums, relying instead on dithering and interpolation (switching rapidly between the two closest gray levels) to expand their 6-bit panels into pseudo-8-bit displays. This often shows up in color accuracy testing on TN displays with one or two colors having a high delta E while the rest are very close to ideal.

Pixel response times are another bloated statistic, with claimed response times of as low as 1ms for some TN panels and most now stating 2ms GTG (gray to gray). In theory, that would mean refresh rates of up to 500 Hz would be possible with no image persistence between frames. While no LCD currently available offers a refresh rate higher than 120Hz - and even those are relatively rare, only recently showing up with NVIDIA's 3D Vision technology - we still see image persistence on every LCD we've tested. That's not to say TN isn't a bit faster, but the difference is small enough that most users won't notice; either the response time will be "slow" on any LCD (relative to a CRT), or else it will be fast enough that you won't care.

Processing lag is potentially related to pixel response time. We don't know for sure if the lag comes after the crystal matrix receives a new voltage or if it comes before the voltage change, but we do know that of the tested panel technologies currently available, PVA seems to suffer the worst in this area by far. We only have one reference point on MVA panels, but we've read other reviews that support the idea that MVA response times are significantly better than on PVA. Processing lag can also come from hardware scalers used to support other resolutions, the prime example being Dell's 3008WFP. Even at native resolution, that display reportedly has anywhere from 10ms to 50ms of processing lag (depending on the revision that was tested). We have not seen any similar issues with other panels, most likely because scalers for lower resolutions have been around for quite a while and have been tweaked for optimal performance.

We also haven't tested any IPS panels outside of 30" LCDs, so we don't know for sure how IPS fares at other resolutions. Given 30" panels command a price premium, they may perform better overall than the smaller IPS displays; however, we believe IPS panels inherently process images as fast as any other LCD technology. Finally, it's worth noting that we have not been able to compare any LCD panel to a CRT for processing lag - we don't have access to any good CRTs anymore for comparison. Anecdotal evidence suggests that the best LCDs may still introduce a 15-30ms lag relative to a CRT. For better or worse, LCDs are here to stay and CRTs are a dying breed, so we'll constrain processing lag comparisons to LCDs and other newer panel technologies (i.e. OLED, SED, plasma, etc.)

Finally, we have to put all of this into perspective by introducing price into the equation. TN panel LCDs are by far the cheapest, often costing half as much as the same size display with an IPS/MVA/PVA panel. Since the non-TN displays do cater more towards professionals, some of the price difference may be artificial, but TN panels are still the least expensive option. They are also the oldest LCD technology, having been around since the dawn of LCDs. As much as you might want a high quality IPS display, when it comes down to a choice between a $400 22" IPS display or a $175 TN display, it's no surprise that a high percentage of people go with the inexpensive TN option.

So which panel technology is "best"? Clearly, it depends on many factors including pricing. Without price, I'd personally take an IPS display over any of the others, but again I may be biased by having only used 30" IPS panels. Many LCD HDTVs also use IPS panels, and given the recent growth in the HDTV market we'd expect there to be a few more improvements in the base technology. Like other displays, however, many HDTVs are now beginning to ship with TN panels, so if you're thinking about getting a new HDTV you'll definitely want to exercise care in what you buy.

Index A Closer Look at the BenQ FP241VW
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  • praeses - Wednesday, June 17, 2009 - link

    After using this particular monitor as my primary display at home for well over a year I have fairly decent experience with it. Nearly all of my concerns are reflected in this review. Having said that there are a few aspects I would like to point out:

    The input lag varies significantly from inputs and resolution. Using DVI at 1920x1200 yields the lowest while analogue at any other resolution is significantly higher. Using any of the different lighting modes adds lag as well. For my purposes I have them turned off.

    VGA also seems to be quite washed out. It has troubles with certain timings as well including XBOX360 where it cannot compensate for the overscan. The composite inputs are reasonable although when scaled any signal distortion is amplified significantly.

    Of course, the fluorescent backlight is annoying. As a previous commenter has implied that using LCDs do not result in headaches, that is far from the truth. Once manufacturers move towards LED backlighting hopefully some of that will be alleviated. To date I have been unsuccessful at tracking down a suitable LED panel to swap into this monitor. The non-adjustable backlighting is also significantly annoying in low light conditions with some bleeding, although fairly consistent throughout the panel appearing gray.

    The headphone connection only working for audio over HDMI just seems silly. They should have included an analogue pass-through.

    Prior to purchasing this monitor I was aware of most of these issues and they are consistent between screens. Some people have buyer's pride and dismiss it or do not see them to begin with. Despite this, I am quite happy with this monitor and have not found a better replacement for my uses where viewing angles, input lag (over DVI), and composite inputs are paramount.
    Reply
  • Spacecomber - Wednesday, June 17, 2009 - link

    I think the reason that the trend with LCDs is simply to make them cheaper and not better has a lot to do with there being no meaningful specifications that the consumer can use to compare one monitor to another. In many cases, you can't even tell what kind of panel is being used. (Imagine buying a CRT monitor and not being able to easily tell whether it was a shadow-mask or an aperture grill tube.)

    With no meaningful information about the monitor in its technical specifications, the only thing the consumer can easily determine is relative price differences.

    At this point, it is pretty clear that the industry manufacturing LCDs has no motivation to redress this on their own. I don't know who might be in the best position try to change this, but outside pressure (if not outright regulation) needs to be applied, if there is any hope of making manufacturers compete on a level playing field, when it comes to what a particular monitor really is capable of.

    I suspect that respected professional computer hardware review publications, such as Anandtech, could wield some clout in pursuit of this end, and I hope that they pick up the banner.
    Reply
  • darklight0tr - Wednesday, June 17, 2009 - link

    I agree. The panel type should be disclosed in the specifications for all LCDs so the consumer knows what they are getting. Right now you have trudge through the bowels of the Internet just to find what panel is being used for a particular display, since most of the time it isn't disclosed.

    The technical specifications are also suspect because the "tests" used aren't standardized or controlled in any meaningful fashion. That's how you can have 2ms LCDs that really are 10ms or higher. Same thing with contrast ratios, especially dynamic ones. I'm just waiting for the LCD that has Infinity:1 contrast ratio. That's the one for me!
    Reply
  • tomoyo - Wednesday, June 17, 2009 - link

    Companies will never do this for one big reason. Profit. They profit from the lack of real specifications on lcds that allows them to make even low end lcds seem to be good. And most people don't care at all. We're the few that actually try to give good advice on avoiding crap lcds, but we can't fight against the huge tide of mindless consumers. Reply
  • JarredWalton - Wednesday, June 17, 2009 - link

    Don't forget the other reason a lot of companies don't like to disclose the type of LCD panel they use: they don't want to be "locked in" to a specific LCD panel. If they were to advertise that the display uses, for example, an S-PVA panel, they wouldn't be able to switch to less expensive TN down the road -- or perhaps IPS or MVA. High quality displays generally don't change panels midway through the production run, but the same can't be said of less expensive models. Reply
  • tomoyo - Wednesday, June 17, 2009 - link

    No kidding. I remember all that panel lottery madness with those Samsung TN-films such as the 226BW. It was ridiculous when there were 4 possible panels you could receive from one monitor model. Same thing with the Dell IPS/S-PVA lottery from long ago. It's dishonest how little they care about the quality of the product that we get.
    I'm glad my friend got a Benq FP241W with a similar MVA panel to the one you just reviewed a couple years ago for around $600. Probably the best pickup for a 24" at the time. (and he was lucky not to experience problems like some have).
    Reply
  • alexdi - Wednesday, June 17, 2009 - link

    The lag numbers for the Dell 2408WFP are incorrect as of revision A01, which replaced A00 four months ago. A01 lag is significantly reduced and identical to the 2407WFP A04. I have had all three screens at once to verify this. Reply
  • fmyhr - Wednesday, June 17, 2009 - link

    http://www.kwiksurveys.com/online-survey.php?surve...">http://www.kwiksurveys.com/online-survey.php?surve...

    If you would like to be able to buy a ThinkPad or other business-class notebook with a premium screen, please take the survey at the above url when you can spare a couple of minutes.


    Survey results are here:
    http://forums.lenovo.com/lnv/board/message?board.i...">http://forums.lenovo.com/lnv/board/mess...al_Inter...


    Thanks for your help!
    Reply
  • GTaudiophile - Wednesday, June 17, 2009 - link

    I spent a few months doing research, trying to find a 24" replacement for my really old DELL 2001FP.

    It more or less came down to the DELL 2408WFP and the HP LP2475w. But I just read too many negative reviews, calibration issues, etc. to feel that either was a safe bet of my $550.00 USD.

    What am I looking for? 24". 1920x1200. 1080P. 16:9. Something "approved" by photographers for photo editing / color accuracy. But something that can also be a decent gaming monitor when needed. Something that will allow me to be on the net for hours without causing too much eye fatigue. And finally costs around $500 or less.

    In the end, I quit my search for now, unsatisfied with current market offerings. If the "Stickied LCD" thread in the Video Cards & Graphics forum is any indication, I am not the only frustrated person out there.
    Reply
  • haplo602 - Wednesday, June 17, 2009 - link

    I want to buy the HP screen you mentioned. What negatives did you find about it ? I did only find favorable reviews. Reply

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