The Best 3D Technology: Stick with Passive Glasses

Dr. Raymond Soneira of DisplayMate Technologies separates the best smartphone, tablet, HDTV, and multimedia displays from the worst with his Display Technology Shoot-Out series. And his newly crowned 3DTV champion might just give you some major 3D buyer's remorse:

The first generation of 3D TVs were launched in the spring of 2010 to tremendous fanfare, but failed to generate enough consumer excitement and retail activity, so the first year sales turned out to be disappointing. There are plenty reasons why this happened: many consumers had recently upgraded to HDTVs and were hesitant to upgrade again to 3D HDTVs. Most new technologies are expensive and often have performance issues—in fact, many of the 2010 3D TVs received mediocre evaluations. There wasn't much 3D content available to watch. Consumers didn't care for the cumbersome and expensive 3D glasses that had to be worn in order to watch 3D TV.

All of the 2010 3D TV models—both LCD and Plasma—required Active Shutter Glasses, which have high-speed LCD shutters for each eye that are electronically synchronized to the sequential right and left images generated by the TV every 1/120th of a second. 2011 has resulted in a lot more available 3D content and two important developments in 3D technology: a new generation of 3D TVs with Active Shutter Glasses, and a new 3D TV technology called Film Pattern Retarder (FPR) that uses very light weight and inexpensive Passive Glasses that are similar to ordinary polarized sunglasses, and identical to the 3D glasses used in most 3D movie theaters. The FPR 3D TV technology doesn't need high-speed electronic shutters because it uses circularly polarized light filters to keep the right and left images separate for each eye.

3D TV technology is still relatively new so it's not surprising that most consumers (and many reviewers) are still trying to sort out all of the manufacturer's claims, figure out what they mean, and what they should do next. There are some conflicting and unsubstantiated statements about 3D TV technologies that are being made in a badgering manner just like in the classic tale of The Emperor's New Clothes. The object of this article is to provide detailed objective test results that will let you decide what is really there, or not there… But the most important issue of all is whether either of these technologies is able to provide an enjoyable and convincing 3D viewing experience – we'll answer that below, but first we'll back it up with lots of objective evidence.

There are a number of very interesting (and frequently misunderstood) 3D imaging and visualization issues that need to be examined for both of these 3D TV technologies in order to straighten out the incorrect and confusing information about them. This article will provide an objective in-depth analysis of both 3D technologies. We have plenty of measurement data, which provides lots of good objective evidence, but the most interesting and important part in evaluating 3D is the actual 3D imaging and visualization itself, and that only happens inside the brain, so instruments cannot help with that part of the evaluation. We used lots of high quality 3D content including 3D movies, photos, images and test patterns. We will describe a series of quantifiable 3D visual tests that anyone can duplicate to verify our results and conclusions on 3D TV imaging for themselves.

Highlights and Summary of Results

This Highlights section has a summary of the most important results of the 3D TV Display Technology Shoot-Out. All of the details including the measurements and analysis are documented within the dedicated sections for each topic. If you are new to 3D, be sure to read our Overview of 3D Vision and Technology and our Overview of 3D Glasses.

The Main Issues

We examined four recent model high-end 3D LCD HDTVs – two with Active Shutter Glasses from Samsung and Sony, and two with FPR Passive Glasses from LG and Vizio. They were set up in a Shoot-Out configuration for detailed simultaneous side-by-side comparisons as shown in Figure 1 below. Details are provided in the 3D TV Models and Shoot-Out section. Both of these competing 3D technologies each have their own set of particular strengths and weaknesses.

For Active Shutter Glasses the main issues are excessive flicker, image crosstalk and ghosting, insufficient brightness, problems with viewing comfort and cost of the glasses. For Passive Glasses the main issues are questioned resolution and sharpness, restricted viewing distances, angles and positions. You'll see many of these issues mentioned in reviews and advertisements. But the most important issue of all is whether either of these technologies is able to provide an enjoyable and convincing 3D viewing experience—we'll answer that below, but first here are the main conclusions from our extensive series of objective tests and measurements.

Summary of Results

For the Active Shutter Glasses we found the flicker quite annoying and tiring, but the Passive Glasses were completely free of flicker, which is discussed in detail in the Flicker section. While not everyone notices the 60 Hz shutter flicker from the Active Glasses, it is still possible to be affected by flicker and not be aware that it is present. Most people can sense flicker at 60 Hz or even above. CRTs were well known sources of 60 Hz flicker – as a result a significant portion of the population may be susceptible to flicker from Active Shutter Glasses. Subliminal flicker, which is flicker just below the threshold of conscious detection, can also cause visual fatigue. There are good reasons for suspecting that a portion of the eye strain associated with 3D TV is the result of flicker and subliminal flicker from Active Shutter Glasses.

The Best 3D Technology: Stick with Passive Glasses

For most viewing angles and viewing positions the Active Glasses also had considerably more Crosstalk and Ghosting, which are not only annoying but more importantly interfere with the 3D imaging and 3D Contrast – the measurements are in Table 2 and are discussed in detail in the Crosstalk and Ghosting with Viewing Angle and Position section.

The Best 3D Technology: Stick with Passive Glasses

Passive Glasses also did considerably better with varying Head Tilt, which is very important during normal TV viewing – the measurements are in Table 3 and are discussed in detail in the Crosstalk and Ghosting with Head Tilt section.

The Best 3D Technology: Stick with Passive Glasses

The Passive Glasses TVs delivered 3D images that were 2½ times brighter than the Active Glasses – the measurements are in Table1 and are discussed in detail in the Brightness Measurements section. The Passive Glasses were also considerably more comfortable to wear, and cost less than 1/5th the price of Active Glasses.

On the other hand, Passive Glasses have a more restricted range of vertical angles and viewing distances, so you can't watch 3D TV closer than about 6 feet from the screen, or watch 3D TV standing up closer than about 8 feet, or watch a 3D TV mounted high up over a fireplace without a tilt mount. None of these affect normal 3D TV viewing in our opinion, and none of them apply to 2D viewing. These issues are discussed in detail in the FPR Viewing Positions and Distances section.

In general, most reviews and evaluations agree fairly well with the above points, but our extensive measurements quantitatively show how much better the Passive Glasses perform under a wide range of typical viewing conditions.

Sharpness and Resolution with FPR Passive Glasses

By far the most controversial and misunderstood issue in 3D TV currently has to do with the sharpness and resolution delivered with Passive Glasses. Because they split the odd and even lines between the right and left eyes it's easy to see why many people (and some reviewers) conclude that FPR technology delivers only half of the HD resolution. However, 3D images have only horizontal parallax from the horizontally offset cameras, so the vertical image content for the right and left eyes are in fact identical – but with purely horizontal parallax offsets from their different right and left camera viewpoints. So there isn't any 3D imaging information that is missing because all of the necessary vertical resolution and parallax information is available when the brain combines the right and left images into the 3D image we actually see. That is the theory and fundamental principle behind 3D Image Fusion for FPR TVs—so next we actually tested it to see how accurate it is and how sharp the 3D images actually appear.

Sharpness and Resolution with Active Shutter Glasses

Active Shutter Glasses also have 3D image sharpness issues, but they instead arise from left-right image Crosstalk that can blur fine detail and muffle the 3D image depth and 3D Contrast. This results from the limited Response Time of the LCD screen and the LCD shutters on the Active Glasses. So both 3D technologies have 3D Image Sharpness issues—so we needed to test them both to see how well they actually do…

Testing 3D Image Sharpness

Because the 3D images are created in the brain, instruments can not be used to measure how sharp or muffled they appear on a given 3D TV – that can only be done with human vision by actually viewing 3D content – but it can be done in a very precise and analytical manner. What matters here is the actual 3D visual performance NOT an analysis of the display hardware diagnostic performance the way it is normally done for 2D displays—and DisplayMate Technologies is considered the world leader in this area by many.

We performed a series of quantifiable sharpness tests by using what is in effect a Reverse Vision Test where we determine display sharpness by how small a text that can be read on a given 3D TV at a given distance when viewing regular Blu-ray movie content. If there is Image Fusion we should be able to read particularly small size text (6 to 10 pixels in height) with the Passive Glasses, but if the Passive Glasses only deliver half the resolution, as some claim, then it will be impossible to read the small text on the FPR TVs. The primary source for our tests was the Blu-ray documentary IMAX Space Station 3D because it has very high quality 3D imaging shot by NASA with an IMAX stereo camera without artificial effects or special effects and the spacecraft has lots of labels and printed signs with small text on the instruments and walls that are great for detailed quantifiable sharpness comparisons.

3D Sharpness Results

The Best 3D Technology: Stick with Passive Glasses

The 3D tests details are documented in the 3D Imaging, Resolution and Sharpness Viewing Tests section, with the results listed in Table 4. They were done at the closest recommended 3D viewing distance of 6 feet. In all cases the small text (6 to 10 pixels in height) was readable on the FPR Passive Glasses, which definitively establishes that there is excellent 3D Image Fusion and the Passive Glasses deliver full 1080p resolution in 3D. Again, if the Passive Glasses only delivered half the resolution, as some claim, then it would have been impossible to read the small text on the FPR TVs. So those half resolution claims are manifestly wrong—no, ands ifs or buts!

Furthermore, in all cases the small text was actually sharper and easier to read and fine details easier to resolve on the FPR Passive Glasses than on the Active Glasses because of the Crosstalk, ghosting and Response Time issues that reduce 3D image sharpness and 3D contrast in Active Glasses TVs.
We also compared the small text 3D visual sharpness to the 2D sharpness by repeatedly turning the 3D mode on and off for each of the TVs and watching in 3D with glasses and then 2D without glasses. In all cases the images were sharper in 2D than in 3D, but the differences were much smaller with the FPR TVs than with the TVs with Active Shutter Glasses. In fact, the small text 3D visual sharpness on the FPR TVs were only slightly less than in 2D, reinforcing our conclusion that the Passive Glasses deliver 3D Image Fusion with full 3D 1080p resolution and are visually sharper in 3D than Active Glasses because of the Crosstalk, ghosting and Response Time issues mentioned above. It's easy enough for anyone to check these results by repeating the visual tests listed in Table 4.

Some reviewers have evaluated 3D TVs by analyzing the combined display hardware performance for the right and left channels instead of the actual 3D visual performance tests that we have done. That simply leads to incorrect conclusions in the case of 3D vision because of Image Fusion in the brain. In fact, based on our own extensive display diagnostic tests it is clear that the FPR TVs have been optimized for the best 3D visual performance instead of the best hardware diagnostic performance – that is most likely why they perform so well with 3D vision. So reviewers and analysts relying on display diagnostics are failing to see the forest for the trees, are simply barking up the wrong tree, and arriving at results that don't apply to actual human 3D vision!

On the other hand, there are instances when 3D Image Fusion may not work well with FPR. They arise when the brain is unable to properly match up the right and left image content or when there is fine computer pixel and line graphics, but they were very seldom noticeable in all of the video Blu-ray content we used for the Shoot-Out. These issues are discussed in detail in the Instances When FPR 3D Image Fusion May Not Work section.

Main Conclusions

Based on our extensive lab measurements and visual test comparisons between 3D TVs with FPR Passive Glasses versus 3D TVs with Active Shutter Glasses, we found that the Passive Glasses TVs delivered substantially and demonstrably better all around 3D imaging, 3D Contrast and sense of 3D depth, better 3D sharpness, better overall 3D picture quality, immersion and realism, and freedom from 3D ghosting, image Crosstalk, and flicker. This was true in all but a small number of situations, all of which we document in the sections mentioned above.

Convincing 3D

One of my favorite examples for demonstrating the differences between the 3D TV technologies is at 10:47 in IMAX Space Station 3D, which shows a protruding glove and orange pipe in front of a deep equipment area with lots of fine image detail. Press Pause on the player. With Passive Glasses you feel that you are right there in the Space Station with a convincing, clear and realistic 3D image that has crisp 3D detail and good 3D Contrast throughout, and without any noticeable visual artifacts. With Active Glasses there is so much large scale Crosstalk that generates ghosts and poor 3D Contrast, and small scale Crosstalk that produces fuzzy 3D that the image looks quite phony – and then there is the annoying flicker from Active Glasses. There are plenty of comparable demonstrative examples in the wide range of 3D content that we viewed. Visually the differences between these two 3D technologies are enormous when compared side-by-side – FPR Passive Glasses TVs provide a substantially higher quality 3D visual imaging and 3D visual experience than the TVs with Active Glasses. Check out this image yourself, and also the other specific examples that we provide in 3D Imaging, Resolution and Sharpness Viewing Tests section.

Enjoyable 3D

The Passive Glasses were quite comfortable and, more importantly, free from the annoying flicker that many people (including the author) experience with Active Glasses. The annoying picture flicker, Crosstalk and ghosting from Active Glasses are the main reasons why many people have previously shunned 3D TV. The lab measurements showed Passive Glasses to perform much better than the Active Glasses, but what genuinely surprised me is that for the first time I really enjoyed watching 3D content with Passive Glasses. Almost everyone that I invited to the 3D Shoot-Out left with the same feeling and many remarked "this is cool" or "this is great!" Avatar was the most requested title for people that came to see the 3D Shoot-out and everyone was just as thrilled by it on the FPR TVs with Passive Glasses as in the movie theaters. Everyone that watched the roller coaster scene in the 3D Blu-ray movie Despicable Me commented on the sensational 3D experience of an actual roller coaster ride. To maximize your enjoyment of 3D be sure to read our Recommendations for 3D TV Viewing section, which explains a number of simple steps that can be taken to improve TV viewing comfort and reduce the likelihood of eye strain and fatigue when viewing 3D (as well as 2D) TVs.

Almost Holographic 3D

One of the most fascinating visual effects of 3D TV is how the 3D image changes as you change your viewing position. If you are looking at a still image in 2D and change your viewing angle by walking left to right in front of the TV, the image of the TV picture produced by the brain stays the same as you move. But when you do that in 3D the picture appears almost holographic because the brain continuously reworks the perspective geometry of the image as you change your viewing position. As a result, people sitting at different locations will see somewhat different perspective geometries of the same 3D image. The effect can grow to be quite large for images with significant depth. It sometimes seems as if you might be able to see additional things that are currently obscured by shifting your viewing position even more, but of course that never happens, you only see an increasingly shifted perspective view. It's one more interesting facet of 3D TV viewing.

The Real Magic of 3D

If you read the consumer 3D movie reviews on Amazon.com people often focus on how big the 3D effects are—which is great for demos and impressing friends, but that wears off soon as a gimmick (and it also causes eye strain). The real magic of 3D in my opinion is when I am watching well produced typically subtle 3D content with Passive Glasses and then feel that I am actually present in the scene, walking on the beach along with the people in the video, for example—an emotional response that results from convincing 3D visual input. Following our recommendations for 3D viewing I experienced virtually no visual fatigue, and absolutely no headaches, dizziness or other adverse effects while watching with Passive Glasses. The Passive Glasses are very light weight, inexpensive and comfortable—they're easy to pop on and off and it's easy to forget that you are wearing them. The Passive Clip-Ons are great for people with prescription glasses. The magic of providing a comfortable, convincing, and realistic 3rd dimension to TV viewing is what will make this 3D technology catch on and become successful in the future. 3D TV has finally come of age and arrived as a fun and pleasant enhancement to watching traditional 2D movies and TV content.

This article has been republished with permission from DisplayMate.com.

About the Author
Dr. Raymond Soneira is President of DisplayMate Technologies Corporation of Amherst, New Hampshire, which produces video calibration, evaluation, and diagnostic products for consumers, technicians, and manufacturers. See www.displaymate.com. He is a research scientist with a career that spans physics, computer science, and television system design. Dr. Soneira obtained his Ph.D. in Theoretical Physics from Princeton University, spent 5 years as a Long-Term Member of the world famous Institute for Advanced Study in Princeton, another 5 years as a Principal Investigator in the Computer Systems Research Laboratory at AT&T Bell Laboratories, and has also designed, tested, and installed color television broadcast equipment for the CBS Television Network Engineering and Development Department. He has authored over 35 research articles in scientific journals in physics and computer science, including Scientific American. If you have any comments or questions about the article, you can contact him at dtso@displaymate.com.

About DisplayMate Technologies
DisplayMate Technologies specializes in advanced mathematical display technology optimizations and precision analytical scientific display diagnostics and calibrations to deliver outstanding image and picture quality and accuracy – while increasing the effective visual Contrast Ratio of the display and producing a higher calibrated brightness than is achievable with traditional calibration methods. This also decreases display power requirements and increases the battery run time in mobile displays. This article is a lite version of our intensive scientific analysis of smartphone and mobile displays – before the benefits of our advanced mathematical DisplayMate Display Optimization Technology, which can correct or improve many of the deficiencies – including higher calibrated brightness, power efficiency, effective screen contrast, picture quality and color and gray scale accuracy under both bright and dim ambient light, and much more. Our advanced scientific optimizations can make lower cost panels look as good or better than more expensive higher performance displays. For more information on our technology see the Summary description of our Adaptive Variable Metric Display Optimizer AVDO. If you are a display or product manufacturer and want our expertise and technology to turn your display into a spectacular one to surpass your competition then Contact DisplayMate Technologies to learn more.