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3D Display Technology: Passive Polarized Vs. Active Shutter

HP 2311 gt 23" Monitor Review: Passive, Polarized 3D On A Budget
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Regardless of the display you use, stereoscopic 3D works by delivering a unique, dedicated image to each eye that represents two different perspectives. Your brain blends them to deliver a sense of depth.

There are really only two commercially-successful 3D display technologies available to PC enthusiasts right now: active shutter systems, which use alternate-frame sequencing to block light to one eye while the other is shown its appropriate image, and passive circularly-polarized systems that let you tilt your head and still maintain left/right separation. The technology HP uses to achieve stereoscopy with its passive display is called film-type patterned retarder, or FPR.

We covered the basics of active versus passive systems in Wall Sized 3D Gaming, Just like The Theatres Do It back in 2010. For the purposes of this article, though, it makes sense to recap the most important differences between passive polarized FPR-based displays and active alternate-frame sequencing-based screens.

Passive 3D (Polarized, Film-Type Patterned Retarder)

This type of display exploits the wave-like properties of light to control what is seen from each eye. It relies on a polarized filter that covers the screen. This filter has two orientations: one for even lines of resolution, and one for odd lines of resolution. Each alternate line displays the output intended for a specific eye. The viewer must wear polarized glasses in order to realize the illusion of 3D; however, the glasses contain no electronic parts—each eye is simply covered by a passive polarized filter. The filter over the right eye blocks out the lines of resolution intended for the left eye, and the filter over the left eye blocks out the lines intended for the right eye. In this way, each eye only receives its intended perspective, even though the output for both eyes are displayed on the same screen at the same time.

This describes the FPR technology used in HP's 2311 gt. Polarized passive displays are also used in a vast majority of movie theatres, but they employ a different method that doesn't halve resolution. If you’re interested, you can read more about that here.

The Benefits Of Passive 3D

Now, let’s consider the implications of FPR-based displays. First, the glasses require no active electronics, so they’re very inexpensive to manufacture and less cumbersome than shutter glasses. They're so inexpensive, in fact, that you’re given a pair every time you go see a move in stereo at the theater. As mentioned, you can even use the glasses from theaters equipped with RealD's technology on HP's 2311 gt.

Second, many folks find polarized displays easier to look at for prolonged periods because they aren't receiving 60 flashes per second from active eye-wear. This seems to predominantly be a case-by-case observation, though, and there are those who aren't bothered by the shutter effect at all.

Also, passive FPR displays allow the user to view the light from the display 100% of the time. This isn't the case with an active shutter-glasses  solution where the aperture is closed half the time in each eye, and brightness is negatively affected.

An FPR-based implementation works at 60 Hz, so a standard HDMI cable has ample bandwidth to enable stereo content. This isn't the case with active systems, which require 120 Hz output to deliver 60 frames to each eye, each second. As a result, using HDMI 1.4, you can only get 60 frames per second at a maximum 720p resolution using shutter-based technology. That doesn't mean you can use any old 3D TV in your living room with a set of polarized glasses. However, as it pertains to polarized monitors like HP's 2311 gt, passive 3D is certainly more accessible. 

Passive 3D's Compromises

So far, polarized stereoscopy sounds pretty awesome, right? Well, there is a significant caveat. Mainly, when it comes to a FPR display, each eye is only treated to every second line of resolution, or, half of the frame. Fine detail is most affected by this, and and small text in a computer game can be difficult to make out. The closer you get to the screen, the more obvious this effect becomes. It is a significant detractor from image quality. As you might imagine, a loss of resolution is more pronounced up in front of a PC monitor than it would be from the couch looking at a 3D-capable television.

In addition, the polarized filter on the screen has to be aimed. And that means there is an optimal viewing angle. If you stray too far from it, severe anomalies like ghosting start cropping up, making the output intolerable.

Active 3D (Shutter, Alternate-Frame Sequencing)

Shutter-based systems that employ alternate-frame sequencing use powered shutter glasses that, as its name suggests, alternately block the output to each eye. With displays operating at 120 Hz, that means each eye gets a smooth 60 frames every second.

An infrared emitter is responsible for sending a signal to the glasses to blank-out every other frame. So, each eye sees a single frame of output and is then covered for the next one, intended for the other eye. At the aforementioned 120 Hz, this happens quickly enough that you don't notice the blanking process. The most noticeable impact is a darker image.

Because the glasses in an active system perform a major role, flipping back and forth, they require power. That means they also need batteries that periodically have to be recharged or replaced. The glasses also host wireless receivers and transparent LCD screens, so they tend to be expensive as well (in the $50 to $150 range). Multiply that out for a family of five, and you're looking at a major variable in the decision whether or not to invest in the technology. Additionally, the loss of light in each eye half of the time is very perceptible. And finally, the glasses are not very elegant, given their active circuitry.

Active displays can deliver true 1080p content to each eye 60 times a second. Unfortunately, the HDMI 1.4 standard doesn’t offer enough throughput to support that quantity of data, though. Consequently, typical 3D televisions are limited to 24 FPS at 1080p. That's fine for a Blu-ray movie, but it's painfully inadequate for smooth gaming. Instead, owners of GeForce graphics cards have to look for 3D Vision-certified monitors. If you have a new-enough Radeon card, an AMD HD3D-certified monitor does the trick, too. AMD's Radeon HD 7000-series cards do support a new "fast HDMI" standard able to serve up 60 FPS at 1080p over HDMI. But with no compatible displays currently available, that feature doesn't figure into today's story.

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  • 17 Hide
    PreferLinux , July 13, 2012 7:38 AM
    f-141950's cheap gimmick idea of what 3-D is.complete false advertising since it's on a 1D screen.save your money.

    You mean 2D.
  • 11 Hide
    army_ant7 , July 13, 2012 10:55 AM
    f-141950's cheap gimmick idea of what 3-D is.complete false advertising since it's on a 1D screen.save your money.

    One thing you have to understand that the fact that even 3D models in a game for example get rasterized to a 2D screen. Are they a gimmick then since 3D or 2D graphics, they still end up being 2D anyway? 3D games give us the perception of a 3D world.
    If these technologies can make us have the illusion of having a 3D view, like in real life, then I wouldn't say it's a gimmick. Are (better) in-game graphics a gimmick? A game world is also an illusion of something that isn't there, just like how it seems that you're saying 3D isn't there because it's a 2D screen.
    BTW, it's 2 different frames from different perspectives shown at the same time, just like how your two eyes work. I assume you have two, if not, I apologize.

    If you don't like stereoscopic 3D, then fine, voice out your opinions, but claiming those opinions of yours as facts is just not right. I don't mean to sound angry, but I felt obliged to "voice" this out. I'm open to debate and I don't mean to piss anyone off.
Other Comments
  • 1 Hide
    army_ant7 , July 13, 2012 5:42 AM
    I forgot if I read this before, but your GPU would have to pump out twice the number of frames for games. As it obviously seems, this is true for active shutter 3D displays. I assume that even if polarized 3D displays "interlace" 2 half resolution frames for 1 3D frame, the processing needed is still for 2 full resolution frames.

    If anyone has better knowledge on this, please correct me. :-)
  • 17 Hide
    PreferLinux , July 13, 2012 7:38 AM
    f-141950's cheap gimmick idea of what 3-D is.complete false advertising since it's on a 1D screen.save your money.

    You mean 2D.
  • -1 Hide
    mayankleoboy1 , July 13, 2012 8:13 AM
    Quote:
    Radeon: Catalyst 12.6 Beta


    dont you mean 12.7 beta?
  • 0 Hide
    vdr369 , July 13, 2012 8:22 AM
    Its not worth the price, and if you compare the quality warranty with AOC 23 inch polarized monitor AOC (which has superior color accuracy and 3 years onsite warranty)knock outs this dummy.

    and I liked the acer's 27inch polarized one because it doesn't need a software to convert 2d to 3d.
  • 11 Hide
    army_ant7 , July 13, 2012 10:55 AM
    f-141950's cheap gimmick idea of what 3-D is.complete false advertising since it's on a 1D screen.save your money.

    One thing you have to understand that the fact that even 3D models in a game for example get rasterized to a 2D screen. Are they a gimmick then since 3D or 2D graphics, they still end up being 2D anyway? 3D games give us the perception of a 3D world.
    If these technologies can make us have the illusion of having a 3D view, like in real life, then I wouldn't say it's a gimmick. Are (better) in-game graphics a gimmick? A game world is also an illusion of something that isn't there, just like how it seems that you're saying 3D isn't there because it's a 2D screen.
    BTW, it's 2 different frames from different perspectives shown at the same time, just like how your two eyes work. I assume you have two, if not, I apologize.

    If you don't like stereoscopic 3D, then fine, voice out your opinions, but claiming those opinions of yours as facts is just not right. I don't mean to sound angry, but I felt obliged to "voice" this out. I'm open to debate and I don't mean to piss anyone off.
  • 0 Hide
    hyteck9 , July 13, 2012 12:19 PM
    what about dual 3D monitors? Do any video cards even support the setup? Would it even be playable?
  • 0 Hide
    army_ant7 , July 13, 2012 12:42 PM
    I think there's a 3 3D monitor setup possible with Nvidia cards. I'm not sure, but if what I've shared in the first ever comment on this thread is true, driving 1 3D monitor is already like driving 2 standard ones. 3 3D's would be like 6 standards.
    AMD cards can drive an Eyefinity of 6 (standard) monitors, so maybe 3 3D's doesn't sound to bad.
    Again, I'm not sure. Just sharing my observations and deductions on this, and I could be very wrong. :-)
  • -1 Hide
    SnickerSnack , July 13, 2012 12:47 PM
    Dual 3D monitors would be unplayable - The inside screen edges would split your character in half 99% of the time.
    Nvidia supports 3D Surround, which is three identical monitors. I haven't seen it in action, but hear it's fabulous. Pretty sure it requires at least a couple of beefy GPUs running in SLI.
  • -6 Hide
    hyteck9 , July 13, 2012 12:50 PM
    I have quad SLi (2x GTX590's) just never tried 3D with em..
  • -3 Hide
    panzerknacker , July 13, 2012 12:55 PM
    I can't see why any serious gamer would use a inferior budget screen like this. I mean common, image quality from those $300 or less screens is just complete trash compared to say a good CRT monitor or plasma tv, so why bother? It's nice when your on a budget but if you spend say $1200 on a serious gaming machine then your not gonna couple it with a $300 monitor. It would be very nice if Tomshardware would review some more serious computer screens sometimes in a higher price range of about $800 or something.
  • 2 Hide
    army_ant7 , July 13, 2012 1:17 PM
    @panzerknacker: Maybe this article isn't just for you. For some people, I bet it is. Some people might not be as picky with image quality (colors, brightness, contrast, etc.) but may still appreciate stereoscopic 3D. It also doesn't have to be gaming, but I'm not saying it can't be. It could be for watching 3D Blu-rays as well. :-)
  • 0 Hide
    MauveCloud , July 13, 2012 1:28 PM
    "we have to consider HP’s 2311 gt an AMD HD3D-only solution"

    You're forgetting to consider third-party 3d drivers, like iZ3D and Tri-Def

    "BTW, it's 2 different frames from different perspectives shown at the same time, just like how your two eyes work. I assume you have two, if not, I apologize."

    One important difference to consider here: human eyes also focus the lenses based on distance, but with a 3d screen (whether active, passive, or even autostereoscopic like the Nintendo 3DS), one's eye lenses have to focus to the screen distance even when the 3d effect is simulating a different distance.
  • -1 Hide
    panzerknacker , July 13, 2012 2:09 PM
    @army_ant7

    Yeah you're right, but what I also try to say is that the last years they almost only review screens like this, cheap ones, and considering this is a website mainly for enthusiasts it would be nice to read about some nicer ones as well!
  • 0 Hide
    army_ant7 , July 13, 2012 2:37 PM
    If that's the case, I'd agree with you there. Maybe they haven't been receiving test samples? Hehe...
  • -1 Hide
    jaquith , July 13, 2012 3:19 PM
    No thanks to passive 3D. In contrast the similar ASUS VG23AH at least offers an IPS panel vs the HP 2311 gt's TN.

    For a few bucks more look at the still not stellar but better ASUS VG236H (~$330).

    Bottom-line, if I have a monitor for years that I'm going to be staring at -- you're Damned Right it's worth spending the extra cash and getting something easy on the eyes. Otherwise it's like getting cheap shoes that are your only pair and suffering.
  • -2 Hide
    cleeve , July 13, 2012 3:59 PM
    panzerknacker@army_ant7Yeah you're right, but what I also try to say is that the last years they almost only review screens like this, cheap ones, and considering this is a website mainly for enthusiasts it would be nice to read about some nicer ones as well!


    Our previous 3D Vision 2 vs HD3D review compared the newest 3D Vision monitor tech with the newest Samsung tech,. There hasn't been any notable changes to the 120 Hz 3d monitor market since.

    http://www.tomshardware.com/reviews/geforce-3d-vision-hd3d-steroscopic,3050-2.html
  • 0 Hide
    Marcus52 , July 13, 2012 4:09 PM
    I must admit to being a bit prejudiced against FPR technology, for the simple reason I want higher refresh rates more than I want 3D, and FPR does nothing to support 120Hz refresh rates.

    Of course for 3D shutter technology, I really want 240Hz (minimum) :)  .
  • -1 Hide
    MauveCloud , July 13, 2012 4:28 PM
    soldier37Tired of seeing these cheap 1080p displays being churned out week to week. Where are the LED 30 inch 2560 x 1600 models at to replace my current LCD model? Get with the program guys. Once you go that size you wont ever want to do 1080p again.


    I mostly agree. I went back to 1080p because my XHD3000 was outputting too much heat into my room, but an LED monitor with that resolution probably wouldn't be so bad. I'm somewhat regretting the 32 inch TV with passive 3d I recently bought (I had underestimated the issues with text based on TFT Central's article that discussed 3d display types :(  ), but I seriously doubt the warranty would let me return it just because I want a higher-resolution monitor. Setting aside obscure South Korean brands like Yamakasi and Achieva, I think the newest super-high-resolution monitor is the Apple Thunderbolt display, but that was released on July 20, 2011, making it almost a year old. Some of the other models are harder to find release dates for, but I think they were 2010 or older.
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