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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  • alantay - Wednesday, June 17, 2009 - link

    "For better or worse, LCDs are here to stay and CRTs are a dying breed"

    A bit off topic to the review itself, but since you mentioned it: At the time LCDs were taking over the market, they were 2-3 times more expensive than CRTs. They absolutely could not compete in speed (input lag was unknown before LCDs came around), they absolutely could not compete in viewing angles (idem), They could not compete in color and contrast, they absolutely could not compete in "natural look" (things look perfectly natural in a CRT monitor and very unnatural in a LCD one). And obviously, they could not compete in price. Yet, 90%+ of the people buying a new monitor were choosing an LCD. Why?

    The obvious advantage of LCDs was exterior design. They're very good looking monitors when compared with the ugly and bulky CRTs. But then again, is exterior design so important for something like a monitor as to pay 3 times more for something 10 times worse??? Oh, LCDs were a new technology, I guess some people also like anything new (even if worse). But...

    Still a mystery to me... (writing this using my -very- old CRT).
    Reply
  • Rindis - Thursday, June 18, 2009 - link

    "The obvious advantage of LCDs was exterior design. They're very good looking monitors when compared with the ugly and bulky CRTs."

    No, the obvious advantage is weight and volume. It is much easier to find a place to park a screen (especially a larger one), when you don't have have as much room in back of it as to the sides.
    Reply
  • strikeback03 - Thursday, June 18, 2009 - link

    Now I'll admit that I never used a top-quality CRT (best I have ever used were some large ViewSonics) but IMO the only advantage they hold over even 5-year old LCDs is the viewing angles (vs TN). LCDs don't vibrate all over the place, they don't need fooling around with the video card to keep refresh rates up, text is actually sharp, and, of course, you can get a decent sized one without worries about lifting it. Reply
  • TA152H - Saturday, June 20, 2009 - link

    CRTs are much better than LCDs at certain things. The reverse is also true.

    If you have very good eyes, looking at an LCD is like looking through a screen door. You can see the small divisions between pixels easily.

    By contrast, CRTs have much richer pictures, without these barriers.

    I hated LCDs, but bought one anyway just to give them a try. When I am using it, I get used to all the flaws of it, and don't mind it at all. Then when I look at a CRT, I'm annoyed by the moire issues, and other irregularities. This is at higher resolutions though, at lower resolutions, the CRT is just better except for logistics. So, I really prefer the LCD when that's what I've been using. But, if I am using a CRT, and then go to an LCD, it looks lifeless and dull, and the screen door issue irritates the Hell out of me.

    Anything at or less than 800x600 is clearly the advantage of the CRT. It's got few if no issues, and has much better color saturation. Above that though, where it really matters, it's really personal preference. No one can say that one is clearly better than the other, they are better at different things and we all have to make a choice (well, it's almost been made for us now). Heck, I can't even say which I prefer. I do like the low glare of LCDs a lot though, but now I see some with mirror like finishes. That's really strange. I don't know why people would want these, especially on a laptop with a lot of ambient light.
    Reply
  • Griswold - Wednesday, June 17, 2009 - link

    No, you forgot the number one reason: no headaches and eyestrain compared to those god forsaken CRTs. Reply
  • The0ne - Thursday, June 18, 2009 - link

    yep, good riddance to those CRT monitors. yay for my eyes! :) Reply
  • JarredWalton - Wednesday, June 17, 2009 - link

    It depends on what you're comparing: a top quality CRT to a typical LCD at launch, yes, the CRT would win in most areas. But...

    LCDs have perfect geometry when using a digital signal, they weigh less, brightness levels look better on most models, and did I mention size? LOL... Actually, the geometry adjustment stuff on CRTs is one thing I'm happy to NEVER have to do again. Trapezoidal, rotational, pincushion, etc. distortion sucked, and you had to adjust for each resolution and refresh rate.

    What I miss - and the only thing I really miss! - is the 100+ Hz refresh rates. Even the current 120Hz LCDs don't generally do a 120Hz signal (that would require dual-link DVI at 1920x1200); they just refresh the content more frequently. (I might be wrong on this - some displays may actually support a 120Hz signal?) Oh, and I suppose I also miss true blacks on occasion, but with most games being developed on LCDs there were times when having "true black" was a problem (i.e. Doom 3 - I thought the game was unplayable until I tried it on my then-new 2405FPW LCD).
    Reply
  • Mastakilla - Wednesday, June 17, 2009 - link

    you are right about most 120hz displays not being really 120hz

    you are also right about real 120hz @ 1920x1200 requiring dual link DVI

    there do exist some REAL 120hz 1650x1080 displays though (I think Viewsonic has one for example)
    Reply
  • TA152H - Wednesday, June 17, 2009 - link

    If you want to find a quality monitor, review an Eizo. They've been the best monitors for 20 years, and you can't compare junk from BenQ, ViewSonic, et al with them. The only problem is cost, but, if you're just focused on quality, nothing comes close.

    Prove me wrong. Review one of their high end monitors and then see if you hit the UPS man over the head when he comes to take it back.

    Once you get used to them, it's a hard habit to break, and an expensive habit to keep.
    Reply
  • erple2 - Wednesday, June 17, 2009 - link

    That was true 20 years ago when we all had CRT's - it was very hard to beat an Eizo / Nanao in picture quality.

    However, the LCD era kind of changed all of that. Eizo makes some nice panels, sure, but they're really not the best. There's a couple of superb NEC monitor out there at the 1200-2200 price range (the 2490 and 3090 models), plus at least 2 HP 24" monitors (the 2475w and 2480zs) that are as good or better than anything Eizo puts out.

    I think the "problem" now is that there are only a few manufacturers of the panels, so there's only so much any reseller can do.
    Reply

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