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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  • tomoyo - Wednesday, June 17, 2009 - link

    AUO seems to have focused on using AMVA and AMVA3 (their latest tech) only on LCD TVs. The only way to get their good stuff is to buy a 32" 1080p LCD TV using their panel. If you look at their current monitor production, it's literally ALL tn-film. Depressing to the extreme.

    http://auo.com/auoDEV/products.php?sec=monitor&...">http://auo.com/auoDEV/products.php?sec=...mp;func=...
    Reply
  • JarredWalton - Wednesday, June 17, 2009 - link

    And the worst part is that the page starts out by talking about how great AMVA is... and then they only have TN panels listed. Ugh.... Reply
  • tomoyo - Wednesday, June 17, 2009 - link

    Going by B5 analogies. Looks like E-IPS is now our last best hope for good LCD panels. S-PVA would interest me more if there was less input lag, but E-IPS seems to have a good chance of giving us good viewing angles + decent panel speed. Now if we could only get LED backlights + 120hz + ergonomic stands in a 16:10 format over a wide variety of sizes, then we'd be in business. I can't imagine that some company out there wouldn't see an opportunity for premium lcd monitors that hardcore gamers/photography/graphics lovers would love to have at moderate prices. I think this area is a completely unrealized market opportunity.

    I also really dislike the 16:9 format for LCD monitors. It's takes away the balance between fullscreen and widescreen that we have with 16:10. Another cost cutting move that annoys me greatly.
    Reply
  • darklight0tr - Wednesday, June 17, 2009 - link

    LED backlights on computer LCDs seem to be a very low priority for manufacturers right now. The focus for that tech seems to be LCD TVs, which is disappointing. I'm beginning to think we'll see OLED computer displays before LED backlight LCDs at the rate they're going! The other problem with the LED backlighting is many manufacturers have been pairing it with TN panels. Its like putting a V8 into an econobox.

    E-IPS looks to be very good, but one of the reasons I went with S-PVA despite the display lag possibility is contrast is a weak point for IPS technology, and that was an important feature to me. Plus, it wasn't widely available in the screen size I was looking for.

    If they make 120hz PC LCDs available, I want it to be TRUE 120hz, not the crap they've been selling with LCD TVs. I've seen "120hz" TVs and its obvious that it is an image processing technology that emulates 120hz, and it looks like crap. My friend has it on his TV, and I had to make him turn it off because it was so distracting.
    Reply
  • erple2 - Monday, June 22, 2009 - link

    To be fair, the bulk of the 120Hz technologies in TV's (particularly flat panel sets) exists solely for de-judder purposes. It conveniently lets you display 24 fps, 30 fps, and 60 fps content at an even multiple.

    My Sony TV is a 120 Hz TV - I think that there are 2 things that it's used for:

    1. "Motion Smoothing" - very cool but super-annoying technology that smooths out and essentially interpolates intermediate frames in slower than 120Hz content. It's somewhat distracting with film - you can think of it as watching a movie, but filmed with a modern high end digital video camera. The "action" is interpolated to appear more than 24 Frames per second. I don't like it.
    2. Solid de-juddering. Since most TV's are 60 Hz, when showing content that isn't an exact multiple of 60, the TV has to do some pulldown to get the image to appear right on the TV (the so-called 3:2 pulldown). The 120 Hz "fixes" that, since you don't need to do any complicated pulldown algorithms to get the proper effect.

    Since there is no 120 Hz content available that you'd normally watch on a TV (games displayed from a very high-performance computer being the only exception I can think of), I think that it's mostly a marketing talking point.

    So, no, generally, the 120 Hz TV's are actually 120 Hz TV's - they do update the display ever 1/120th of a second. However, given LCD's inability to fully RENDER a new pixel that fast is a whole 'nuther issue. 120 Hz translates to 8.333 ms response time necessary to actually change the image on screen.
    Reply
  • darklight0tr - Wednesday, June 17, 2009 - link

    On top of all that there has been a disturbing move to 16:9 displays. I know they are trying to standardize things, but I really like the extra real estate offered by 16:10. I guess I'm going to have to keep my DELL 2709W until something amazing comes along or it explodes. Reply
  • hyc - Thursday, June 18, 2009 - link

    Second that. I want a 42" 1920x1200 monitor to replace my living room TV, but no such beast exists, they're all 1920x1080. Talk about frustrating.

    The interesting thing about "voting with your wallet" is you can only vote from a selection of what the manufacturers offer you, there's no way to vote for a new product that none of them currently offer. These days, my wallet has been staying closed...
    Reply
  • tomoyo - Wednesday, June 17, 2009 - link

    The market for LCDS has been terrible for over a year now. Basically all the high quality non-tn films have been discontinued with a few rare exceptions. Also all the high quality height adjustable stands are mostly gone, which makes it almost impossible to put lcds in a position that doesn't cause back/neck/carpel tunnel/etc issues. It's idiotic what we have these days.

    I'm lucky I have two older dell models that are non-tn film at work and a similar one at home, all with adjustable stands. 1905FP and 2001FP to the rescue. Sadly I can't even imagine changing these out for any new model, because in general the new models are WORSE. I consider myself stuck with these models until a miracle happens.

    Now for a secondary screen, generally the best solution I've found for a good panel is to get a 32" LCD TV 1080P. That's one of the only ways to get a moderately usable screen at a low price, which also has FAR more inputs than any Lcd monitor. You can't get $600 Lcd Monitors that are 32" with 3-4 hdmi inputs and massive amounts of composite/component/s-video. The only huge negative is the low resolution, but 1080P is certainly liveable and great as a secondary video watching device.
    Reply
  • BugblatterIII - Wednesday, June 17, 2009 - link

    I've got a Dell 2407WFP but that's being reallocated so I'm planning to get the Dell 2407WFP. H-IPS screen, portrait rotation, fantastic quality, low latency etc Reply
  • BugblatterIII - Wednesday, June 17, 2009 - link

    Of course I meant planning to get the HP LP2475w. Reply

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