We've been talking about stereoscopic 3D for a while now. We have it in our living rooms and on multi-display stands in our lab. In fact, based on the Tom's Hardware offices around the world, you might even guess that this technology is gaining a foothold. But away from our test benches, we can count on one hand the number of friends and family who considered 3D a compelling-enough experience to buy.
Although stereoscopic 3D hasn't caught on the way many vendors hoped it would, we're not entirely surprised. The premium on screens, powerful-enough graphics cards, and active shutter glasses remains significant. And when folks aren't bowled over by what they see, it's hard to charge more for it.
Nevertheless, we make an effort to keep up with the technology. We published the world’s first introduction to Blu-ray 3D on the PC, and more recently dug into a thorough comparison of Nvidia’s 3D Vision and AMD’s HD3D initiatives. There is a topic we haven't weighed in on yet, though: the two most prolific 3D viewer technologies for achieving stereoscopy, active shutter and polarized passive systems.
When Hewlett-Packard let us know that it wanted to send over its new 2311 gt 3D monitor, sprung at the chance to evaluate HP's hardware and compare a passive solution to the 120 Hz active options we've used in the past.
HP 2311 gt 3D Monitor

More than a year ago, we reviewed HP's 2311x in Three-Way 23" LED LCD Roundup: Dell, HP, And Samsung. The budget-oriented 23" TN-based LCD sported a 1920x1080 native resolution, plastic construction, and easy display input accessibility thanks connectors that stuck straight out the back of the monitor.
The 2311 gt is modeled after the 2311x, a fairly strong hint that the 2311 gt targets an entry-level customer interested in stereoscopic 3D. A quick look at its price is all of the confirmation we need: at the time of writing, this screen costs $250 on HP's website after a rebate (its list is $300). That's one of the lowest prices for a 3D-capable screen we've seen.

For the price, you get the same monitor chassis as HP's 2311x. It's both plastic and light, with a solid base that doesn’t allow for height, swivel, or pivot adjustments. Tilt can be set from 90 to about 65 degrees from the desktop (tilt is a critical adjustment for Film-type Patterned Retarder 3D technology, and this is something we’ll talk about later). Despite its limited available adjustments, the monitor feels sturdy-enough.

As a reviewer, I can appreciate that the 2311 gt's display inputs are easily accessible, presenting HDMI, DVI, and VGA connectors straight out the back. This makes it easier to attach cables without getting up under screen. And while those straight-out-the-back inputs would likely interfere with a wall-mount configuration, this display isn't designed to support such a set-up, so that's a non-issue.

The on-screen display is controlled by four buttons on the bottom-right corner of the LCD. The menu includes basic output adjustments like contrast and brightness, but goes a step further when it comes to color management by facilitating custom red, green, and blue levels set by the viewer. This is a good thing, too; the sample HP submitted had high blue and green levels according to our Spyder 2 Pro calibration equipment, which suggested we set the monitor to 255 R, 195 G, and 160 B.

Bundled with the screen you'll find a power adapter and cord, a six-foot HDMI cable, and a CD loaded up with documentation and software. The disc includes CyberLink’s PowerDVD for Blu-ray 3D playback and 2D-to-3D DVD/video conversion, along with TriDef 3D software for rendering PC games in stereoscopic 3D. That's all you need for playback and gaming in stereo, aside from the actual content. Of course, you get other extras, such as monitor drivers, the HP adjustment pattern utility, and twenty-five demonstrative 3D photos.
Lastly, the box comes with two pairs of passive FPR glasses with protective pouches and a cleaning cloth. It’s important to note that these light, simple, and low-cost polarized glasses represent one of the primary strengths of passive 3D displays. The 2311 gt even works with the RealD 3D glasses you may have been handed at a movie theater and LG's branded FPR 3D glasses.

| HP 2311 gt Specifications | |
|---|---|
| Part Number | QJ684AA |
| Panel Type | TN |
| Viewable Image Area | 20.047" x 11.276" |
| Dimensions (HxWxD) | 21.97"x6.26"x16.4" |
| Weight | 3.7 kg |
| Viewing Angle | Horizontal 170o, Vertical 160o |
| Brightness | 200-250 nits |
| Contrast Ratio | 1000:1 |
| Response Rate | 5 ms |
| Color Gamut | 72% |
| Native Resolution | 1920x1080 @ 60 Hz |
| Pixel Pitch | 0.265 x 0.265 mm |
| Pixels Per Inch (PPI) | 96 |
| 3D | Film-type Patterned Retarder (FPR) |
| Power Consumption | 45 W |
| Warranty | Limited One-Year warranty |
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.
One of what we consider to be the biggest potential benefits of passive polarized screens is, in theory, full support for both Nvidia’s proprietary 3D Vision standard (via 3DTV Play) and AMD’s HD3D open standard. HDMI is ample for 60 FPS gaming at 1920x1080 on a passive display because the visual information needed for both eyes is available in one frame of video. That is to say, it doesn't require 120 Hz to facilitate 60 FPS. The obvious caveat is that vertical resolution is halved.
When it comes to testing the theory behind this, AMD’s HD3D does deliver stereoscopic 3D at 1920x1080, 60 FPS over HDMI on HP's 2311 gt without a problem. Nvidia's 3D Vision/3DTV Play solution, on the other hand, does not work.
We mistakenly assumed that Nvidia’s 3DTV Play would recognize and work on the HP display. However, the recent 301.42 driver build was unwilling to enable the feature when we plugged in Nvidia's 3D Vision emitter. A little research revealed that the company's drivers are somewhat picky when it comes to the displays they'll allow 3DTV Play to recognize.
A workaround on the MTBS3D Forums and 3D Vision Blog pointed to a possible solution: force the monitor to utilize a driver from an Nvidia-supported model, such as Acer’s HR274H. To our surprise, this trick appeared to give HP’s 2311 gt full 3D Vision support, even without Nvidia's emitter plugged in. Unfortunately, even though our setup passed the built-in driver test, we couldn’t to get it working in a real-world game. The 2311 gt simply reported an out-of-range error.
As a result, we have to consider HP’s 2311 gt an AMD HD3D-only solution when it comes to stereoscopic 3D gaming. This isn’t a big surprise; it's not touted as 3D Vision/3DTV Play-compatible. Nevertheless, we're somewhat disappointed, particularly because limited compatibility narrows the market for HP's monitor.
As far as comparing AMD's HD3D initiative to Nvidia's 3D Vision standard, check our coverage on them both in Nvidia 3D Vision Vs. AMD HD3D: 18 Games, Evaluated and Stereo Shoot-Out: Nvidia's New 3D Vision 2 Vs. AMD's HD3D. To summarize them, both solutions work well, but certain titles are more refined under one solution or the other. So, if you're interested in playing a game on HP's 2311 gt, you might want to cross-reference it with the GameGrade3D database at MTBS3D.com.
The PC we're using for testing isn’t particularly important. However, the second 3D monitor we're comparing HP's to is. We have Samsung’s S23A750D, an active 3D monitor able to help emphasize the differences between the HP 2311 gt’s FPD-based technology.
As we began writing this review, Samsung’s S23A750D sold on Newegg for $310, but was recently deactivated. The most similar product that is available is the Samsung S23A700D, a panel with almost identical specifications, but no DisplayPort input.
| Test System | ||||||||
|---|---|---|---|---|---|---|---|---|
| CPU | Intel Core i7-3960X (Sandy Bridge-E), 3.3 GHz, Six Cores, LGA 2011, 15 MB Shared L3 Cache, Hyper-Threading enabled. Overclocked to 4.25 GHz | |||||||
| Motherboard | ASRock X79 Extreme9 (LGA 2011) Chipset: Intel X79 Express | |||||||
| Networking | On-Board Gigabit LAN controller | |||||||
| Memory | Corsair Vengeance LP PC3-16000, 4 x 4 GB, 1600 MT/s, CL 8-8-8-24-2T | |||||||
| Graphics | Reference Radeon HD 7970 925 MHz GPU, 3 GB GDDR5 at 1375 MHz | |||||||
| Hard Drive | Samsung 256 GB (SSD) | |||||||
| Power | ePower EP-1200E10-T2 1200 W ATX12V, EPS12V | |||||||
| Software and Drivers | ||||||||
| Operating System | Microsoft Windows 7 x64, Service Pack 1 | |||||||
| DirectX | DirectX 11 | |||||||
| Graphics Drivers | GeForce: 301.42 WHQL Radeon: Catalyst 12.6 Beta | |||||||
| Monitors | ||||||||
| Passive (FPR) | HP 2311 gt | |||||||
| Active (AFS) | Samsung S23A750D | |||||||
Let’s consider the image quality of HP's 2311 gt circularly-polarized display compared to Samsung's 120 Hz active solution. Although we can't give you an accurate depiction of stereoscopic 3D on these monitors, we can take pictures through the glasses bundled with each to demonstrate some of the strengths and weaknesses each exhibits when it comes to brightness, ghosting, and clarity.
Brightness
When it comes to brightness, HP's 2311 gt is significantly better than the 120 Hz solution. This is because the polarized glasses allow light to pass through 100% of the time, while the active implementation alternately blanks out each eye half of the time.

This is obvious in the animated GIF above. The photographs of each display were taken using the same manual camera settings through the glasses provided with each monitor. HP's 2311 gt enjoys a clear advantage in this area.
Ghosting And Viewing Angle
The 3D filters on a passive, polarized screen must aim the 3D effect at an ideal viewing position. If you leave that position, it's probable that you'll see images in one eye intended for the other, resulting in an effect called ghosting. Moreover, polarized filters are not 100% efficient. So, you could end up with ghosting even from the optimal position. An active shutter-based system doesn't suffer the same artifact; you're able to view the screen from a wider range of angles without ghosting.
The HP 2311 gt’s ideal viewing distance seemed to be about 2.5 feet from the display; that's where its 3D effect really popped out. Everyone is comfortable at different distances away from their monitor, and I'm usually about a foot and a half away from my 23" screen, necessitating that I sit farther away than I like.
Although shifting left or right has little effect on the 2311 gt's viability, moving up or down as little as four inches from 2.5 feet away caused massive ghosting anomalies. The monitor does support tilt adjustment, so it's not hard to rectify angle-dependence. However, you are compelling to viewed the screen from one position. And if you have multiple people looking at the monitor, they all need to be on the same plane relative to you. The following animated GIF illustrates:
Even positioned optimally, the 2311 gt suffers from minor ghosting, while Samsung's 120 Hz panel doesn't. As an aside, both displays seem to get a bit brighter when you look at them from higher-up.
Clarity
Polarized displays look their best if you're watching a movie on them from the comfort of your couch. When it comes to PC monitors, however, you're typically quite a bit closer. In this case, a lack of clarity can become a real problem.
It’s very easy to notice that you only see every other line on the 2311 gt, especially when it comes to fine detail and tiny text. The TriDef 3D driver has a soft interlacing option that helps clarify hard-to-read text from within games. But it's still hard to swallow what you see below from HP's 2311 gt.

Contrast that with Samsung's 120 Hz display, which offers impeccable clarity in 3D mode.
We should point out that the still shots in the animated GIF were taken through one lens from each set of 3D glasses. It'd be logical, then, that with both eyes receiving information from the display that you'd end up with the full 1080 lines of aggregate resolution. In reality, though, the experience is even more distracting than the GIF suggests. Clarity is one of the biggest problems we have with the 2311 gt when it's used for 3D gaming.
Image Quality On The Windows Desktop
The polarized filters on HP's 2311 gt have a subtle, yet discernible, effect on output, even in 2D mode without the glasses on, particularly when it comes to solid colors. It’s minor, and perhaps easy to ignore for some. However, if you spend a lot of time in the pure white backgrounds of Microsoft Word, your eyes will almost certainly catch the difference between a 120 Hz panel like Samsung's and HP's polarized solution.
Still photographs don't capture the visual impact of polarization very well, so we don't have a good screen shot to show you. But we can assure you that non-polarized monitors do not demonstrate the same issue, since they aren't equipped with the same filters.
I was at a trade show a while back, and Battlefield 3 playing a big-screen television using passive stereoscopic 3D. Attendees were kept behind a line several feet back from the display. It looked great, and I asked the presenter if he was achieving full 1920x1080 to each eye, or if each eye was only getting half-resolution. He replied “does it look like full HD?” Touche! From that distance, looking at that specific content, I couldn’t tell the difference.

You don't use a 3D-capable monitor from 10 feet away, though. It's viewed from much closer distances. And that's where an FPR-based polarized screen is going to have the hardest time excelling, almost entirely because each eye only gets half-resolution. But HP's 2311 gt has to do its job under those tough conditions. Fortunately, 3D movies look pretty good from the proper distance and orientation. Games are usually tolerable, though they're made more annoying when small environmental details and text play an important role.
To be fair, HP's pricing reflects the 2311 gt's market position. Available for $250, the 2311 gt costs about $100 less than a similarly-sized 120 Hz display, which is fairly appropriate for an entry-level FPR-based 3D-capable monitor. It even offers a handful of strengths compared to shutter-based systems, such as much more affordable replacement glasses, significantly brighter output, and no 24 Hz frame rate cap in games over HDMI at 1920x1080. It’s a good choice for folks who want to dabble in stereoscopic 3D without spending a lot of money. The brightness issue alone makes it a viable choice in environments awash with ambient light that can't be controlled. It also performs moderately on the Windows desktop.
For discerning gamers hankering to sample a stereoscopic experience, a 120 Hz screen with active shutter glasses is most definitely the way to go on the PC, assuming that's in your budget. Passive, polarized screens make the most sense in a living room setting, where the distance between you and the display is greater. Playing back movies, predominantly, you're less likely to have to suffer through distorted text. Moreover, families with rambunctious kids will appreciate the low cost of replacement glasses.
