3D TV Display Technology Shoot-Out

Dr. Raymond M. Soneira

President, DisplayMate Technologies Corporation

Copyright © 1990-2011 by DisplayMate Technologies Corporation. All Rights Reserved.

This article, or any part thereof, may not be copied, reproduced, mirrored, distributed or incorporated

into any other work without the prior written permission of DisplayMate Technologies Corporation

Article Series Link:  Display Technology Shoot-Out Article Series Overview and Home Page

 

Introduction

The first generation of 3D TVs were launched in the spring of 2010 with a 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 at home to verify our results and conclusions on 3D TV imaging for themselves.

 

Because some aspects of 3D TV technology are so controversial, and because of the substantial amount of incorrect and misleading information that has been published on this topic, I have provided a considerable amount of detail and analysis for those who are interested in understanding the fine points and verifying the conclusions. For the quickest overview just read the Main Conclusions, for somewhat more detail and analysis read the Highlights and Summary of Results. To read the entire article start at the Overview of 3D Vision and Technology.

 

Outline of the Article with Links

Highlights and Summary of Results

Main Conclusions

Overview of 3D Vision and Technology

Overview of 3D Glasses

Brightness Measurements

Flicker

Left-Right Crosstalk and Ghosting

Crosstalk and Ghosting with Viewing Angle and Position

Crosstalk and Ghosting with Head Tilt

3D Imaging, Resolution and Sharpness Viewing Tests

You Can Easily Do Your Own 3D Visual Sharpness Tests at Home!

Recommendations for Viewing 3D TVs

 

 

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 Summary of Results 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. In fact, most people ran their CRTs at 75 or 85 Hz or above because of flicker, so 60 Hz flicker is a firmly established phenomenon – 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.

 

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. 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 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. Although unsubstantiated it still seems to have evolved into some sort of myth based on hearsay instead of actual scientific visual evaluation. Many people seem to get stuck on this particular issue and can’t get beyond it and think about what is really being seen in actual 3D vision.

 

But it’s not that simple because we watch TV from a far enough distance that the lines are not resolved and we know that the brain combines the images from both eyes into a single 3D image (the one we actually see) in a process called Image Fusion. The 3D TV 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 3D image 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 3D tests details are documented in the 3D Imaging, Resolution and Sharpness Viewing Tests section, with the results listed in Table 4. They were all 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. We show below that it’s easy enough for anyone to check these results at home 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 when viewing natural photographic and video content 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 have their heads in the sand, are failing to see the forest for the trees, are 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.

 

You Can Easily Do Your Own 3D Visual Sharpness Tests at Home!

We have backed our conclusions with lots of solid evidence, but you don’t need to take our word for it because it’s very easy for anyone with a 3D TV and Blu-ray player to perform the same 3D visual sharpness tests at home – so you can actually settle the 3D TV Sharpness Controversy yourself! You just need a high quality source of natural 3D content – the best one by far is 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 has lots of very fine image detail that are fantastic for evaluating 3D sharpness. If you don’t have this particular title use any 3D Blu-ray movie – live is better than animated – use any 3D movie that you have. Be sure to follow our Recommendations for 3D TV Viewing section. If it’s convenient for you to do the tests at the minimum 6 feet viewing distance do so only if you are comfortable with that close viewing distance.

 

The simplest test is just to compare the 3D visual sharpness and contrast to the 2D sharpness and contrast. Pick a scene that has lots of fine image detail and press Pause on the Blu-ray player. Then repeatedly turn the 3D mode on and off for the TV and watch in 3D with glasses and then in 2D without glasses. Every 3D TV has a remote control button that lets you do this easily. Compare the image sharpness and image contrast in 2D and 3D. In all cases the 2D image will be sharper, but flip between them a few times to see exactly what the differences are visually.

 

The best test is to look at the small text examples in IMAX Space Station 3D that we identify in Table 4 with their time positions on the disc so you can find the exact scenes with the small text. Repeat the same 3D to 2D visual comparison but now compare the readability of this very small text. If you have an FPR TV with Passive Glasses then you can verify for yourself that it delivers 3D visual sharpness that is close to the 2D 1080p sharpness. For complete details see the 3D Imaging, Resolution and Sharpness Viewing Tests 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 TV 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…

 

 

Figure 1.  Panoramic View of the 3D Shoot-Out with the Lights Turned Up

 

 

Overview of 3D Vision and 3D TV Technology

The concepts behind 3D vision are both incredibly simple and complex at the same time. Incredibly simple because they are based on the different images seen by the right and left eyes as a result of their separation. The closer an object is the greater the difference in perspective between the right and left eye images. Objects that are very far away have almost identical perspective with similar images for both eyes. The perspective difference between the right and left images is called Parallax. But what happens next is amazing – the brain through incredibly complex processing of the right and left eye images combines them in a process called 3D Image Fusion that creates a single visual image (the one we actually see) along with a sensation of depth for everything within the image – depth perception is truly our sixth sense.

 

So it’s actually quite easy to produce 3D content – just show appropriately different images to the right and left eyes and the brain automatically generates the 3D image. The most straight forward method is to use two identical cameras that are offset horizontally from one another. It needs to be done that way because most of the time our heads are level so the eyes are oriented exactly horizontal and are expecting content with that same horizontal parallax orientation. But some care is necessary in producing 3D content because our eyes and brain are designed for processing 3D images that occur naturally in the real world. That is especially true for artificial computer generated 3D content but it also applies to camera 3D content as well. Unnatural 3D content, especially with exaggerated 3D effects or that inadvertently contain false visual cues within the image can lead to visual fatigue and headaches caused when the brain is asked to process unnatural 3D images that it is not accustomed to dealing with. At the end of the article we will provide a number of recommendations for maximizing TV viewing comfort and minimizing eye strain together with some recommendations for content producers.

 

3D TV Technology

Standard 2D TVs show a single image that is updated 60 times per second (Hz). So 3D TVs need to show two separate right and left images at the same 60 Hz rate. That doubling is challenging for both the display and electronics. Currently there are two approaches in the consumer marketplace:  TVs with Active Shutter Glasses produce 120 frames per second and use the shutters to alternately switch the appropriate images to each eye – so each eye gets 60 frames per second. TVs with FPR Passive Glasses use a micropolarizer that applies alternating polarizations to every other raster line on the display. The Passive Glasses are optical filters that only allow the appropriate polarizations through for each eye. Each technology has its own set of challenging issues that we will examine in detail below.

 

While many people believe that a TV’s ability to produce extreme 3D is the true test of 3D performance and quality, the exact opposite is true. It is the small and subtle 3D right and left image differences that are the most technically difficult for any 3D technology to accurately reproduce. That is also what is required to generate realistic 3D because in the natural world 3D is based subtle visual cues and differences. We’ll discuss this in more detail below.

 

Figure 2.  The 3D TV Models of the Shoot-Out

 

The 3D TV Models and Shoot-Out

The object of this study was to provide a completely independent scientific objective assessment of 3D technology for LCD TVs. So 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, which are listed below. We didn’t examine 3D Plasma TVs, but they all use Active Shutter Glasses that are virtually identical to the LCD models, so our conclusions regarding their flicker, comfort, convenience, and cost apply to them as well. All of the testing, evaluations and analysis were done entirely by the author in the DisplayMate Technologies Labs.

 

The Shoot-Out

The four TVs were set up side-by-side in a Shoot-Out configuration for detailed visual comparisons and measurements – see Figure 1. All were simultaneously fed identical 1920x1080x24p frame packed digital signal content using a Kramer Electronics 3D HDMI Distributor connected to a 3D Blu-ray player for movies and a PC with an NVIDIA 3D graphics board and NVIDIA 3DTV Play software to deliver our set of DisplayMate 3D test patterns, test photos and images.

 

The TVs are all 46-47 inch recent high-end models carefully selected for comparable performance and purchased new through retailers. Three of the units are LED Backlight 240 Hz Refresh Rate TVs that are close in price. The 4th unit was a much less expensive Vizio CCFL Fluorescent Backlight 120 Hz Refresh Rate FPR model that delivered impressive performance for its price.

 

The 3D TV Models

Samsung UN46D7000L  $1900  –  Active Glasses not included  –  $250 extra for 2 pairs.

LED Backlight with 240 Hz Refresh Rate.

Additional Samsung glasses range from $50 to $150 per pair. We selected the two top models.

Total price for the Samsung TV and 4 pairs of 3D Glasses is $2150.

Note that Samsung sometimes runs a promotion that includes 2 free pairs of their $50 glasses.

 

Sony KDL-46HX729  $1650  –  Active Glasses not included  –  $140 extra for 2 pairs.

LED Backlight with 240 Hz Refresh Rate.

Additional Sony glasses are $70 per pair or $140 for 2 pairs.

Total price for the Sony TV and 4 pairs of 3D Glasses is $1930.

 

LG 47LW6500  $1710  –  FPR Passive Glasses included  –  4 pairs with TV.

LED Backlight with 240 Hz Refresh Rate.

Additional LG glasses are $25 for 2 pairs.

Clip-On Passive Lenses for prescription glasses are $20 per pair.

Glasses are interchangeable with Vizio FPR and Real D movie glasses.

Total price for the LG TV and 4 pairs of 3D Glasses is $1710.

 

Vizio E3D470VX  $898  –  FPR Passive Glasses included  –  2 pairs with TV.

CCFL Fluorescent Backlight with 120 Hz Refresh Rate.

Additional Vizio glasses are $26 per pair or $45 for 2 pairs.

Glasses are interchangeable with LG FPR and Real D movie glasses.

Total price for the Vizio TV and 4 pairs of 3D Glasses is $943.

 

Calibration

Normally we first calibrate TVs for optimum picture quality before testing them. Since this article is only about 3D imaging we limited the set of adjustments to those that could influence the 3D conclusions. All of the TVs were placed in their “Standard” picture mode. The TVs all have a large number of advanced picture processing controls that continually adjust the picture in real-time in order to jazz up and manipulate the on-screen image. These are a hindrance rather than a help because they interfere with the 3D imaging tests. So we disabled controls like Dynamic Contrast because they detracted from our 3D evaluations. The only significant calibration adjustments that we made were to the “Contrast” controls because most of the TVs had them set too high in order to maximize brightness, which then washes out the image detail due to intensity scale compression. We used our DisplayMate Multimedia Edition calibration software and the Spears & Munsil Blu-ray calibration disc to make sure that we could resolve digital intensities up through level 250 for the lab tests and Blu-ray movie content. As a result, the peak brightness of the TVs were reduced somewhat, but we are much more interested in image detail than brightness.

 

 

Overview of 3D Glasses

One of the biggest obstacles for 3D technology has always been the special glasses that are needed to see the desired content in 3D. That’s because the right and left eyes need to be shown different images in order to create the 3D visual effect. Although there are displays that can produce 3D images without glasses when watching from a single “sweet spot” or a limited range of viewing positions, glasses are currently necessary for the typical extended home TV and movie theater viewing conditions. This is unlikely to change in commercial products for many years. The new 3D TV technologies are a tremendous step up and improvement over the old but still in use Anaglyph 3D glasses with Red and Blue/Cyan (or Magenta and Green) lenses that separate the right and left eye images. The colored lenses make true color images impossible and the 3D effects mediocre because the glasses can not maintain complete separation between the right and left images, an effect called Crosstalk.

 

The new 3D technologies still face the same questions:  do they deliver good color and 3D imaging? Are the glasses light weight, easy to put on and take off? Are they comfortable enough so that you forget you have them on? Do they interfere with the social nature of TV watching with family and friends? Are they stylish or ugly? Is it possible to walk around the house with them on? Can they be used with prescription glasses? How expensive are they? Do they introduce artifacts or other issues that degrade picture quality?

 

Figure 3.  Photos of the Active Shutter and Passive 3D Glasses

 

Active Shutter Glasses

The Active Shutter Glasses used by both LCD and Plasma TVs contain an impressive amount of electronics that include independent LCD shutters for each eye, an infrared or radio receiver for synchronization with the TV, a battery, charging and processing circuitry. That’s why they are expensive. One important point to note is that each 3D TV manufacturer uses their own proprietary Active Shutter Glasses technology so you need to buy their brand of Active Shutter Glasses, although there are aftermarket companies that sell Active Shutter Glasses compatible with multiple brands.

 

We will analyze the 3D imaging and optical performance of the Samsung and Sony Active Glasses later but here are their feature comparisons:

 

Samsung’s 2011 Active Glasses are pretty impressive:  they are reasonably light (1.1 – 1.4 ounces) and have their electronics and battery inside the portion of eyeglass legs that wrap over the ears. The more expensive $150 3700CR model looks fairly stylish and works reasonably well with many prescription glasses. All 2011 models have a Bluetooth receiver that is paired with a particular TV so multiple 3D TVs can be used nearby without interference. Bluetooth communication is much more reliable than with the first generation infrared receivers that lose synchronization if the infrared control beam gets blocked. In addition the glasses have a motion sensor that automatically turns them on when you pick them up and it is possible to buy a wireless charging station instead of using an inconvenient USB charging cable. They turn off automatically after a few minutes if no motion or no Bluetooth signal is detected. On a couple of occasions the glasses shut down unexpectedly when people watched with their heads too still – so we advised everyone to move their heads occasionally. Running time is claimed to be 40 hours on a single charge. The current models cost from $50 to $150 each.

 

Sony’s 2011 Active Glasses are a big disappointment compared to the Samsung models. They look like a pair of large swimming goggles, are quite bulky, heavy (2.1 – 2.2 ounces) and very uncomfortable because of all of the stiff plastic they contain. They will fit over many prescription glasses but then are even more uncomfortable. They still use an infrared receiver that can lose synchronization when the infrared beam gets blocked. They require pushing a power on button and using a USB cable charger, but the TV won’t charge the glasses when it is turned off. Running time is claimed to be 30 hours on a single charge. They cost $70 each or $140 for two pairs.

 

Active Glasses are particularly susceptible to reflecting light directly into the viewer’s eyes from ambient lighting that is behind or above because their lenses are perfectly flat LCDs that have low average transmission when turned on – both of these factors maximize the effect. Some of the glasses have built in shades around the lenses while others include snap on shades in case the effect is bothersome. The Samsung 3700CR is more susceptible than the other models because of its very open nature. The best solution is to turn off all ambient lighting that is above and behind the viewers.

 

Functionally the Samsung and Sony Active Glasses are very similar. Both operate with a right-left switching frequency of 120 Hz. In fact, when both TVs were driven simultaneously with an identical video signal from the HDMI Distributor it was possible to watch both TVs at the same time using either pair of glasses – with just one amusing (or annoying) feature – as a result of a phase shift, the right and left images would periodically flip with respect to one another. When that happens the depth ordering of objects in the image also flips as well, so objects appearing in a front to back arrangement on one TV would appear in back to front on the other, and vice versa.

 

Since 3D Plasma TVs use Active Shutter Glasses that are virtually identical to the LCD models, all of the above issues apply to them as well.

 

FPR Passive Glasses

The FPR Passive Glasses all have functionally identical circular polarizing filters, all are very light (0.6 to 0.7 ounces), very comfortable, and are much less expensive than the Active Shutter Glasses. They simply look and feel like a pair of lightly tinted glasses. You can wear them permanently around the house – everything will look perfectly normal, including you. It’s easy to forget that you have them on and they don’t interfere with the social aspects of TV watching the way Active Shutter Glasses do. Some models have curved lenses and others flat lenses. Note that these glasses are not dark enough to be used as sunglasses and do not offer uv protection.

 

The differences in 3D imaging and optical performance for all of the FPR Passive Glasses that we tested were relatively minor. The primary differences between them come down to personal preferences based on comfort, style and price.

 

There are many people who don’t like 3D movie theaters or 3D TVs because the 3D glasses are not comfortable or wearable with their prescription glasses. Fortunately for them, FPR Passive Glasses are also available as Clip-On models that work very well with just about all prescription glasses. We had a number of people try them out during the Shoot-Out and all were pleased with them.

 

LG has Passive Glasses models that cost $25 for 2 pairs. The Clip-Ons cost $20 per pair. We also had a rim-less designer model by Alain Mikli that was quite popular with many of the women. Vizio has two Passive Glasses models:  Basic and Premium Theater Glasses. The Premium Glasses cost $26 each or $45 for two pairs.

 

The FPR Passive Glasses are also functionally identical with Real D movie glasses. While many movie theaters allow you to take the glasses home (and add them to your FPR collection) we did the reverse and brought FPR Passive Glasses to the movie theater and found them to be more comfortable and better quality for watching movies, especially the rim-less designer model mentioned above. Note that the FPR Clip-On models mentioned above can be used in Real D movie theaters, which should help people with prescription glasses enjoy 3D movies a lot more.

 

 

Brightness Measurements

3D TVs also work perfectly as 2D TVs for traditional TV content. In fact, 3D TVs typically produce better 2D picture quality than ordinary 2D-only sets because they have better displays and processing electronics. But note that any picture quality problems that appear in 2D will also affect the 3D picture quality. All of the tested TVs performed well in 2D and had comparable 2D picture quality.

 

All of the tested 3D TVs are quite bright when producing 2D pictures. The 2D Peak Brightness (technically referred to as Luminance) values measured after calibration with a Spectroradiometer are shown in Table 1. They fall in the range of 350-450 cd/m², which is very bright for most home viewing conditions except when there is sunlight in the viewing area. In fact, they are so bright that for evening viewing or controlled ambient lighting it is important to lower the brightness to avoid eye strain and visual fatigue. All of the TVs offer some form of Automatic Brightness control, but they still need a manual adjustment based on personal visual preferences.

 

But when the TVs are producing 3D their brightness is much lower than for 2D:

 

Active Glasses:  For the TVs with Active Glasses there are two reasons for the decrease in brightness:  first, the TV’s 240 Hz Refresh Rate involves a repeating sequence of 4 sub-frames:  left eye image, black frame, right eye image, black frame. The black frames are introduced to reduce contamination between the right and left eye images, an effect called Crosstalk that produces ghost images. In addition to being annoying Crosstalk muffles the 3D visual effects. The black frames are needed due to the limited Response Time of the LCD pixels, which don’t change quickly enough when switching between the right and left images. The 4 sub-frame sequence results in only 25 percent of the 2D Peak Brightness being provided for each eye. Second reason:  the light also needs to go through the LCD shutters in the Active Glasses and they only allow about half of the light to pass through when the shutter is open. So for Active Glasses in 3D mode each eye only gets to see about 12.5 percent of the 2D peak Brightness. The actual measured values are shown in Table 1.

 

FPR Passive Glasses:  For the TVs with FPR Passive Glasses there are also two reasons for the decrease in brightness:  the TV Brightness remains the same as in 2D, but the polarized glasses block half of the raster lines, so only 50 percent of the 2D Peak Brightness is provided for each eye. Second, the light transmission of the circularly polarized light through the Passive Glasses is about 80 percent. So for FPR Passive Glasses in 3D mode each eye gets about 40 percent of the 2D Brightness – which is roughly 3 times the throughput of the Active Glasses. The actual measured values are shown in Table 1.

 

Table 1. Measured 2D and 3D Brightness (Luminance)  –  Larger is Better

 

From the bottom row of Table 1 we see that the TVs with Active Glasses have approximately 1/3 the Brightness of FPR Passive Glasses, so they need to be viewed under relatively dark ambient lighting.

 

A few months ago I came across an article which claimed that Luminance measurements for 3D TVs might be inaccurate (for unspecified reasons) and therefore might not be a good way to compare the visual brightness for the different 3D technologies. So I decided to actually test that hypothesis by interactively adjusting the Backlight controls on the TVs so that all of the screens appeared to be equally visually bright according to just my eyes looking through the 3D glasses. When I was done making the visual brightness adjustments for all of the TVs I measured their Luminance with the Spectroradiometer and glasses to check the consistency and accuracy of the visual and measured brightness. The agreement was excellent with an error of just 7 percent (Standard Deviation of the Mean), establishing that Luminance is in fact an accurate way to determine visual brightness for these two very different 3D TV technologies.

 

The TVs have one other important difference that that is related to Brightness – the Samsung and Sony Active Glasses TVs both have very glossy screens that reflect back an image of everything in the room, which interferes with viewing the TV picture unless the area is very dark. The tested FPR TVs, to their credit, have matte screens that muffle reflections and make it much easier to view the picture when there is ambient lighting in the viewing area. It’s shocking that manufacturers are still using glossy screens. Hopefully Samsung and Sony will switch to matte screens in the near future…

 

 

Flicker

Flicker results when the eye senses that the brightness is not steady but time varying. LCD TVs don’t generate any inherent flicker when producing 2D images because they all have an Active Matrix of TFT Thin Film Transistors that hold every pixel steady until it is updated in the next refresh cycle.

 

Active Glasses – Picture Flicker:  TVs with Active Glasses suffer from several forms of flicker. Because the LCD shutters in the glasses switch at 120 Hz each eye gets light at half that rate or 60 Hz. Under the “right” circumstances most people can sense flicker at 60 Hz or even above. CRTs were well known sources of 60 Hz flicker. In fact, most people ran their CRTs at 75 or 85 Hz or above because of flicker, so 60 Hz flicker is a firmly established phenomenon – as a result a significant portion of the population may be susceptible to flicker from Active Shutter Glasses. The LCD shutters are fully closed 50 percent of the time, which accentuates the periods of light and dark and therefore increases flicker. But it’s even worse because the TV image brightness for each eye actually has an on duty cycle of only 25 percent. So flicker from Active Shutter Glasses should be more prevalent than in CRTs. These effects produce noticeable picture flicker or shimmer for many people (including the author) and is a major source of visual discomfort and fatigue that can cause headaches, and for some dizziness and other symptoms that are listed in the legal disclaimer pamphlets included with the TVs. While not everyone notices flicker, it is still possible to be affected by flicker and not be aware that it is present. 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 Glasses. It’s important to be on the lookout for any sort of visual discomfort when watching 3D (or 2D) TV. Be sure to read our recommendations for maximizing TV viewing comfort and minimizing eye strain at the end of the article.

 

Active Glasses – Ambient Light Flicker:  Electric lighting doesn’t normally produce visible flicker because its brightness varies at 120 Hz, twice the power line frequency. Unfortunately, that is virtually identical to the Active Glasses shutter frequency, so the two of them beat against one another to produce noticeable flicker because of their phase differences. Fluorescent and Compact Fluorescent bulbs can produce noticeable flicker if they light up any part of the TV viewing area. They should be turned off when watching 3D with Active Glasses. Incandescent bulbs typically produce less flicker with Active Glasses because of their thermal inertia, but note that using them with light dimmers will increase flicker because they work by reducing the power duty cycle.

 

Since 3D Plasma TVs use Active Shutter Glasses that are virtually identical to the LCD models, all of the above conclusions regarding flicker most likely apply to them as well.

 

FPR Passive Glasses:  TVs with FPR Passive Glasses don’t produce any image flicker or ambient light flicker because the screen images are refreshed in exactly the same way as in 2D and the Passive Glasses don’t have any active switching elements so they don’t modulate any of the light intensities. FPR TVs are flicker free.

 

That always present and annoying picture flicker is one reason why many people have previously shunned 3D TV (including the author). The flicker free 3D from FPR Passive Glasses is a major advantage. Next we consider Crosstalk and then Sharpness and Resolution issues and other differences between the two 3D TV technologies.

 

 

Figure 4.  Photo Demonstrating 3D Crosstalk and Ghosting through the Sony Active Glasses

From IMAX Space Station 3D

 

 

Left-Right Crosstalk and Ghosting

By far the most important aspect for producing good 3D is making sure that the right and left eyes see only their intended images – so they don’t detect any image content intended for the opposite eye. Such contamination is called Crosstalk. In addition to being annoying it muffles the 3D visual effects and causes eye strain because the Crosstalk produces ghost images that have zero parallax, which conflicts with the parallax in the main image. When there is a large 3D effect with lots of parallax, the two eye images are then noticeably separated, so the ghosts appear as distinct double images. When the 3D effect is smaller and more subtle, like most of the time in the natural world, the two right and left images appear close together and then the Crosstalk makes the image fuzzy, which attenuates the 3D information and depth effect. The amount of Crosstalk can be measured with a Spectroradiometer peering through the 3D glasses. The ratio of Luminance contamination between the eyes is called the Crosstalk Ratio – the larger the ratio the better. Crosstalk and Ghosting are most annoying and easily seen in images that have high contrast or strong colors with large parallax offsets, but they are actually more destructive of 3D imaging when they affect small parallax offsets that are not easily noticed visually.

 

 

Crosstalk and Ghosting with Viewing Angle and Position

With 2D you can watch any good quality LCD TV from a wide range of viewing positions and viewing angles. All four of the tested 3D TVs performed better than most 2D-only TVs in this regard because they have better LCD panels. If your mother once told you not to sit too close to the TV, she may have been thinking ahead to 3D because when you are watching 3D, the 3D imaging, Crosstalk and eye strain depend much more on viewing angle, position and distance.

 

Viewing Distance

The closer you sit to the TV the greater the field of view and the greater the immersive experience. But you shouldn’t sit too close when watching 3D because it’s more likely to cause eye strain from vergence and accommodation virtual image depth effects. We’ll discuss this in a later section.

 

The manufacturers provide varied distance recommendations:  the LG documentation recommends a viewing distance of at least twice the diagonal screen size, which for 47” is 7.8 feet. The Vizio documentation recommends a viewing distance of 6 to 9 feet with 7.5 feet called optimal for the 47” model. The Samsung documentation recommends a viewing distance of 6 to 20 feet (no mention of screen size) and the Sony documentation does not mention viewing distance.

 

The best viewing distance will vary from person to person – a compromise between visual immersion and eye strain. You’ll need to experiment to find the best 3D viewing distances for yourself, but note that it can vary with the content you are viewing – if there is a lot of exaggerated 3D and Out of the Screen effects you may need to sit further away than when watching more subtle 3D like in the movie Avatar. I had no problems watching most 3D content from only 6 feet, but for some content I found 8 feet reduced eye fatigue. Since the average home TV viewing distance is around 9 feet that is probably a better all around compromise for everyone.

 

Viewing Positions

The best viewing positions for 3D are when the middle of the screen is at eye level. This provides the best 3D imaging and immersive experience. It’s no surprise that the best viewing position of all is right at the exact center with a straight ahead view, but watching from any position within 30 degrees of center still provides good 3D. If you are 6 feet from the TV, ±30 degrees will include everyone on a 7 foot sofa, at 9 feet there is a 10 foot long sitting area. It’s even better if people are spread out in a circle in different seating.

 

Because of the way the brain processes 3D information, viewers at different viewing angles will see somewhat different perspective views of the same 3D image. The effect can be quite large when a scene has significant depth. We discuss this in detail below.

 

Vertical Viewing Angle

When the middle of the screen is not at eye height then the screen needs to be tilted so that it is perpendicular to the line of sight for optimal 3D viewing. If it isn’t the difference is called the vertical viewing angle. If people, especially children, are watching 3D while sitting on the floor then they need to sit further back to keep the angle small (see below) or you need a tilt mount for the TV. A tilt mount is essential if you have put the TV high up, like over a fireplace. Be sure not to combine Vertical Angles with off center Horizontal Viewing because their combined Crosstalk and perspective effects are cumulative.

 

Crosstalk with Viewing Angle

The best 3D imaging is when the TV is being viewed straight ahead at eye level. This provides zero degrees horizontal and vertical viewing angles to the center of the screen and produces the least amount of Crosstalk and Ghosting. That provides the best 3D viewing as discussed above. We measured the Crosstalk by using a Spectroradiometer peering through the right and then left lenses of the 3D Glasses together with 3D test patterns. The ratio of brightness to leakage in the opposite eye is the Crosstalk Ratio – the larger the better. It’s similar to Contrast Ratio, but for 3D. Table 2 shows the measured values.

 

For typical Horizontal and Vertical Viewing Angles the Passive Glasses have a much better Crosstalk Ratio than the Active Glasses, and as a result produce better 3D imaging and less visible ghosting, as shown in Table 2. This is true at 0 degrees and for all horizontal angles up through at least 30 degrees (the largest angle we measured, which is typical for living rooms). This was easy to see in the viewing tests as well, which are discussed in a later section.

 

For Vertical Viewing Angles Passive Glasses perform better only up until about 20 degrees, when their Crosstalk increases rapidly. For larger vertical angles Active Glasses perform much better, but viewing 3D TVs at larger Vertical Angles is not recommended in order to maintain satisfactory 3D Imaging and to minimize eye strain. This is especially important when off center Horizontal Viewing is also involved because their combined Crosstalk and perspective effects are cumulative. Using a tilt mount for the TV can bring the Vertical Viewing Angle down to 0 degrees. 10 degrees corresponds to a child sitting on the floor at 6 feet from the TV when it’s on a standard 22” high TV stand, which is the largest vertical angle anyone should experience when watching 3D TV.

 

FPR Viewing Positions and Distances

The FPR TVs do have some viewing constraints that do not affect normal 3D TV viewing, but it is important to know what they are. These constraints do not apply when watching 2D. For normal straight ahead viewing (without a tilt mount) the vertical eye level for FPR TVs should be between the top and bottom of the screen when watching close by from a distance of 6 feet, otherwise the 3D Crosstalk will increase significantly. So it’s better not to watch 3D TV standing up, which you shouldn’t be doing anyway. But if you really want to, and are 6 feet tall, then just watch from at least 8 feet away. Also, for proper FPR 3D Imaging it is important not to watch 3D TV from closer than 6 feet for proper 3D Image Fusion, which will be discussed in detail below. You shouldn’t be doing that anyway due to eye strain from vergence and accommodation virtual image depth effects. Note that these constraints do not apply to watching 2D images and do not affect normal 3D TV viewing.

 

Table 2. Measured 3D Left-Right Crosstalk Ratio with Viewing Angle  –  Larger is Better

 

The FPR Black Matrix is Not Visible

The FPR LCDs have a larger separation between adjacent TV lines than the other LCDs in order to properly register the micropolarizer and also increase the range of vertical viewing angles before the 3D Crosstalk becomes large. It is implemented by making the Black Matrix mask that surrounds all pixels on all LCD panels a bit thicker between adjacent lines for the FPR LCDs. I have read several instances where the visibility of the Black Matrix has been mentioned without actually checking to see if it’s true under actual TV viewing conditions. So I decided to measure it and settle the issue…

 

Using a high power magnifier that has a 0.1mm reticle I measured 0.55mm for the pixel-to-pixel distance (called the pixel pitch) and 0.20mm for the thickness of the FPR Black Matrix. So the Black Matrix for the FPR units is roughly 36% of the pixel pitch, which is essentially the same size as the individual Red, Green and Blue sub-pixels that make up each pixel, 33%. All of the TVs have this same sub-pixel pitch. So when I look at all of the TVs (including the Samsung and Sony) close up, I can see the Red, Green and Blue sub-pixel stripes only when I am 2 feet or closer from the screen. The same applies to the Black Matrix on the FPR TVs. At roughly 2.5 feet and beyond I am unable to see the sub-pixel structure or the Black Matrix. That is true for both 3D and 2D – so the FPR Black Matrix is invisible for all normal TV viewing distances of 6 feet or more as discussed above. This should settle the issue once and for all…

 

 

Crosstalk and Ghosting with Head Tilt

When watching 2D TV you can tilt your head any way you like and it won’t affect the picture (unless you are looking at an LCD with linearly polarized sunglasses). When you are watching with 3D Glasses both the Brightness and Crosstalk will vary depending on how much you tilt your head. We’ll discuss the effect of Head Tilt on 3D imaging and depth perception below. The best viewing results are obviously with no Head Tilt (0 degrees). But unless your head is in a vise its tilt is likely to vary by 15 to 30 degrees during normal TV viewing. 45 degree Head Tilt is typical when leaning on something like a pillow, and if you lie down on a sofa your Head Tilt is 90 degrees. The measured values for both Brightness (as a percentage) and Crosstalk Ratio are shown in Table 3.

 

Active Glasses:  There are significant performance differences between the Samsung and Sony Active Glasses with Head Tilt. For the Sony Glasses there is a rapid increase in Crosstalk with angle – at a mere 15 degrees the Crosstalk Ratio falls from 59 to 14, a 76% decrease. At 45 degrees Head Tilt each eye sees equal amounts of the right and left images, and at 90 degrees the right and left images are interchanged, which produces 3D depth inversion. It’s shocking that Sony is shipping anything with such poor 3D performance. What’s even more incredible is that the problem is easily fixed by merely adding a linear polarizer to the glasses (not rocket science). Sony may have done this because an extra polarizer lowers the light transmission and brightness by roughly 15 percent. On the other hand, Samsung Glasses do have the polarizer, so their Crosstalk Ratio remains relatively constant with angle (it actually increases slightly) but the 3D Brightness decreases with Head Tilt angle – which is a lot better than the behavior of the Sony Glasses.

 

FPR Passive Glasses:  For the TVs with FPR Passive Glasses the Brightness remains unchanged for all angles up through 90 degrees, and the Crosstalk Ratio remains fairly high until 45 degrees, when it falls to a value comparable to Active Glasses at 0 degrees tilt. In fact, Passive Glasses continue performing even at a full 90 degrees Head Tilt, which is what happens when you watch TV lying down. While the FPR and Passive Glasses continue to work all the way to 90 degrees, the brain’s 3D vision starts fading above 45 degrees. The reason is that as the head tilts the brain is expecting the 3D parallax to follow along with the eyes but the TV only produces horizontal 3D parallax, so depth perception fades away and you only see a 2D image when lying down.

 

Table 3. Measured 3D Brightness and Crosstalk Ratio with Head Tilt  –  Larger is Better

 

 

Figure 5.  Scene from IMAX Space Station 3D on the Samsung TV without 3D Glasses

 

 

3D Imaging, Resolution and Sharpness Viewing Tests

So far we have concentrated on the 3D technology and measurements. But the real bottom line here is how well do these 3D TV technologies perform in delivering convincing, comfortable, enjoyable and high quality 3D imaging and viewing experiences. Since 3D vision occurs in the brain, the instruments cannot take us any further, but it is still possible to objectively evaluate 3D imaging by watching carefully chosen 3D content. What’s more, some of this is quantifiable as we demonstrate below.

 

3D Imaging

For the 3D Imaging tests we used a wide selection of 3D Blu-ray movies and some DisplayMate computer based 3D test patterns. We watched over a dozen movies while following the Recommendations for 3D TV Viewing section, including live action (Avatar, Tron Legacy, and Alice in Wonderland – all of which use post-production 3D effects), IMAX documentaries (Space Station 3D, Hubble 3D, Grand Canyon Adventure 3D, Deep Sea 3D, and The Ultimate Wave: Tahiti 3D), animated features (Despicable Me 3D, Legend of the Guardians 3D, and Open Season 3D). We also watched 3D Aquarium and Sports Illustrated Swimsuit 3D.

 

The IMAX documentaries were the best sources for testing 3D realism and imagery because they are the closest to natural 3D and have the fewest special effects. Space Station 3D and Hubble 3D have by far the finest image details for evaluating and demoing the performance of 3D TVs. 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. The other live action movies were good primarily for evaluating how much better (or worse) 3D is as a TV viewing experience. The animated features were fabulous for experiencing the limitless possibilities of computer generated imagery. Everyone that watched the roller coaster scene in Despicable Me commented on the sensational 3D experience of an actual roller coaster ride.

 

All of the TVs produced good large scale 3D visual effects and 3D images, but they also displayed the 3D issues that we have discussed in the previous sections. In particular, both of the Active Glasses TVs had noticeable picture Flicker and much more Crosstalk and Ghosting than the Passive Glasses TVs. The Sony Glasses were so sensitive to head tilt that we consider them unacceptable for watching 3D. (If you have a Sony 3D TV consider getting aftermarket Active Shutter Glasses).

 

3D Perspective Visual Effects

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 and 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…

 

One of my favorite examples of this effect 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 and change your viewing position by ±45 degrees and see how the perspective geometry fluidly changes dramatically as you move. Two other excellent examples are at 22:18 and 33:17.

 

3D Imaging and 3D Picture Quality

The image at 10:47 in IMAX Space Station 3D is also one of my favorite examples for demonstrating the superior visual 3D Imaging and 3D picture quality provided by FPR TVs with Passive Glasses. 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 the 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 immense when compared side-by-side – FPR TVs with Passive Glasses provide a substantially higher quality 3D visual image and 3D visual experience than the TVs with Active Glasses. Try this and the other comparisons we list yourself…

 

3D Sharpness and Resolution

As we mentioned in the introductory 3D TV Technology section, large scale 3D visual effects and 3D Imaging are fairly easy for any 3D technology. It is the subtle 3D effects based on fine image details and small scale parallax that are the most technically difficult for any 3D technology to accurately reproduce. Each of the 3D TV technologies have their own particular challenging issues:  for 3D TVs with Active Glasses the problem is the limited Response Time of the LCD when rapidly switching between the right and left images, which causes small scale Crosstalk that muffles fine 3D structure and detail. For 3D TVs with Passive Glasses the problem is that each eye only receives half of the 1080 lines in the image. We will take up this latter technically very interesting and widely misunderstood topic first.

 

FPR Resolution and Image Fusion

Because FPR TVs provide only 540 lines to each eye, it’s easy to see why many people (and some reviewers) conclude that FPR technology delivers only half of the HD 1080 lines resolution. That conclusion is reinforced when you walk up close to an FPR TV wearing Passive Glasses and see the gaps between the odd and even TV lines in each eye. But it’s not that simple because we watch TV from a far enough distance that the lines are not resolved and we know that the brain combines the images from both eyes into a single 3D image (the one we actually see) in a process called Image Fusion. Many people seem to get stuck on this particular issue and can’t get beyond it and think about what is really being seen in actual 3D vision.

 

The theory and fundamental principle behind full FPR vertical resolution and sharpness is that the 3D TV 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. So as long as the viewing distance is sufficient so that the raster lines are not visually resolved (for 20/20 vision the visual resolution is 1 arc min, which corresponds to 6.1 feet for a 47 inch TV) the brain should fuse the images from the right and left eyes into a single full 1080p resolution 3D image. One important detail to note is that there are actually two entirely equivalent odd-even and even-odd line pairings for both the right and left FPR images, so both FPR TVs alternate between them at their full Refresh Rate. This also eliminates image artifacts that would result from picking just one pairing or the other.

 

That is the theory and principle behind 3D Image Fusion for FPR, so now we need to actually test it to see how accurate it is and how sharp the 3D images actually appear. This can not be evaluated with instrumentation or cameras  –  only visually  –  but it can be done in an analytic and systematic fashion with objective quantifiable results that anyone can duplicate at home to verify our results and conclusions on 3D TV imaging and sharpness for themselves. Here’s how…

 

Figure 6.  Example of 3D Sharpness Evaluation Using Small Image Text in IMAX Space Station 3D

These are Direct Screen Shots That Are All Taken Without Any 3D Glasses

This is the Largest Text Size Example from Table 4. On-Screen Text Height is Approximately 5mm or 10 Pixels.

 

3D Sharpness and Resolution Viewing Tests

The best way to evaluate 3D Sharpness and Resolution, including FPR Image Fusion, is by comparing and measuring fine image details on different TVs by watching carefully chosen 3D content. The method we use is in effect a Reverse Vision Test. In a standard vision test eye sharpness is evaluated by seeing how small a text you can read on a printed eye chart at a fixed distance. In a Reverse Vision Test 3D image sharpness is evaluated by how small a text or fine image details can be read or resolved on a given 3D TV at a fixed distance.

 

An excellent source for visually evaluating image sharpness and 3D Image Fusion is 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 (2) there is a tremendous amount of very fine image detail in the equipment in the NASA lab facilities on Earth and on the Space Station that are fantastic for evaluating sharpness and image detail (3) there are lots of labels and printed signs with small text throughout the spacecraft walls and instruments that are especially useful for precisely evaluating sharpness by examining how readable the small text is on each of the TVs.

 

In many cases the text is too small to be resolved on any of the TVs. But we found that we could resolve on-screen text as small as 3mm in height at a viewing distance of 6 feet on the TVs. This corresponds to text as small as 6 pixels. On IMAX Space Station 3D we found 14 instances of readable text between 3 and 5mm in height corresponding to 6 to 10 pixels in height at the full 1080 HD resolution. If there is Image Fusion we should be able to read this particularly small text (6 to 10 pixels in height) on the Passive Glasses, but if the Passive Glasses only deliver half the resolution, as some claim, then it will be impossible to read this small text on the FPR TVs.

 

At the points on the Space Station 3D Blu-ray disc that had interesting fine image detail we paused the Blu-ray player, recorded the time positions on the disc, which are listed in Table 4 below, so that anyone can find the same exact scenes and check and verify our results and conclusions. Table 4 lists the disc times, the actual text we found (which can be anywhere on-screen), the pixel height of the text, whether is was readable on the FPR Passive Glasses, and which 3D technology delivered the sharpest and most readable image of the small text. The tests were all done at the closest recommended 3D viewing distance of 6 feet.

 

In all 14 cases the small text (6 to 10 pixels in height) was readable on the FPR Passive Glasses. This definitively establishes that there is excellent 3D Image Fusion and the Passive Glasses deliver full 1080p resolution. 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!

 

What is even more interesting is that in all cases the small text on the Passive Glasses was actually sharper and easier to read and the fine details easier to resolve than on the Active Glasses. This is the result of Crosstalk, ghosting and Response Time issues that reduce image 3D sharpness and contrast in Active Glasses TVs, which have been discussed in earlier sections. Because Passive Glasses are sharper and also have much less Crosstalk than Active Glasses they also deliver significantly better 3D imaging and a much better 3D immersive visual experience as we concluded above.

 

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 in 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. We show below that it’s easy enough for anyone to check these results at home 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 when viewing natural photographic and video content 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 have their heads in the sand, are failing to see the forest for the trees, are barking up the wrong tree, and arriving at results that don’t apply to actual human 3D vision!

 

3D Visual Image Fusion Examples

At 5:08 there is small 5mm high text on the screen (roughly 10 pixels high) that says "CONTROLLED WORK AREA" on a sign in the foreground. See Figure 6. When close up to the FPR TVs, the screen (without wearing the FPR Passive Glasses) showed the expected odd-even staggered lines of the text image for the right and left eyes. Looking up close through the FPR glasses I saw the broken up text until I reached 5.5 feet from the screen, where the image "magically" fused visually in my head and I saw a single 3D image of sharp readable text. This fusion distance is consistent with my slightly better than 20/20 vision. At our standard 6 to 8 feet viewing distances the image text was noticeably sharper and easier to read on the FPR TVs than on the Active Glasses TVs. This definitively establishes that there is good 3D Image Fusion occurring with FPR and that it delivers full 1080p resolution not the half 540p resolution that some reviewers have indicated. The reason for the lack of sharpness on the Active Glasses TVs has to do with Crosstalk from the limited Response Time of the LCD screen and the LCD shutters on the Active Glasses.

 

Another type of 3D imaging test with an interesting set of examples are the Astronaut's family snapshots posted on the spacecraft walls, which appear as collections of small photos in the background. There are a total of 16 snapshots at 33:17 and 33:39. It is possible to make out lots of well defined details within these small snapshots and use them as a measure of sharpness. In all cases it is possible to make out much more photo image detail within the snapshots on the FPR TVs than on the Active Glasses TVs – for example the facial details:  eyes, nose and mouth were much easier to make out on the FPR TVs. Again, this definitively establishes that there is good 3D Image Fusion occurring with FPR and that it delivers full 1080p resolution. Again, the reason for the lack of sharpness and detail on the Active Glasses TVs has to do with Crosstalk from the limited Response Time of the LCD screen and the LCD shutters on the Active Glasses.

 

Table 4.  3D Sharpness Viewing Tests in IMAX Space Station 3D

Readability of tiny text in videos is an excellent measure of display image sharpness in 3D

 

You Can Easily Do Your Own 3D Visual Sharpness Tests at Home!

We have backed our conclusions with lots of solid evidence, but you don’t need to take our word for it because it’s very easy for anyone with a 3D TV and Blu-ray player to perform the same 3D visual sharpness tests at home – so you can actually settle the 3D TV Sharpness Controversy yourself! You just need a high quality source of natural 3D content – the best one by far is 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 has lots of very fine image detail that are fantastic for evaluating 3D sharpness. If you don’t have this particular title use any 3D Blu-ray movie – live is better than animated – use any 3D movie that you have. Be sure to follow our Recommendations for 3D TV Viewing section. If it’s convenient for you to do the tests at the minimum 6 feet viewing distance do so only if you are comfortable with that close viewing distance.

 

The simplest test is just to compare the 3D visual sharpness and contrast to the 2D sharpness and contrast. Pick a scene that has lots of fine image detail and press Pause on the Blu-ray player. Then repeatedly turn the 3D mode on and off for the TV and watch in 3D with glasses and then in 2D without glasses. Every 3D TV has a remote control button that lets you do this easily. Compare the image sharpness and image contrast in 2D and 3D. In all cases the 2D image will be sharper, but flip between them a few times to see exactly what the differences are visually.

 

The best test is to look at the small text examples in IMAX Space Station 3D that we identify in Table 4 with their time positions on the disc so you can find the exact scenes with the small text. Repeat the same 3D to 2D visual comparison but now compare the readability of this very small text. If you have an FPR TV with Passive Glasses then you can verify for yourself that it delivers 3D visual sharpness that is close to the 2D 1080p sharpness.

 

Instances When FPR 3D Image Fusion May Not Work

3D Image Fusion works very well with FPR almost all of the time with the wide range of movie content that we viewed, but there are situations where it doesn’t work well and may produce some visible artifacts. That’s generally acceptable because they are seldom noticeable and every technology has at least some occasional issues and limits.

 

3D Image Fusion may not work well when there is insufficient image context to allow the brain to pair up the parallax from the right and left eye images. With FPR that happens when there is content with very thin nearly horizontal line structures that occur in high contrast situations. For example, in IMAX Space Station 3D you occasionally see some moiré and jagged lines from the thin white edges of the solar panels when they appear almost horizontal, and also with the thin white cables on the Shuttle bay doors when they also are almost horizontal – both against the blackness of outer space in high contrast. Examples are at 3:37 and 6:52 for the solar panels and 3:10 and 11:20 for the cables. In all of these cases the jagged line artifacts are barely noticeable unless you are searching for them.

 

For similar reasons FPR performs best when displaying natural photographic and video content rather than (artificially generated) computer graphics that contains line drawings, tables or any other fine single pixel content because they don’t provide sufficient context to allow the brain to pair up the parallax from the right and left eye images. On the other hand photographic content is loaded visual contexts, so that’s why FPR works very well with virtually all photos, videos and movies.

 

 

Recommendations for Viewing 3D TVs

There are a number of simple steps that can be taken to maximize TV viewing comfort and reduce the likelihood of eye strain and fatigue for viewing 3D TVs. Many of them apply to normal 2D viewing as well.

 

Position:  set the center of the TV as close to eye height as possible – use a tilt mount if it isn’t. The principal viewing positions should be close to straight on and not at a large viewing angle. Orient the TV to minimize reflections from room lighting, windows and sunlight. If that is not possible use window treatments to control exterior light.

 

Ambient Lighting:  make sure the ambient lighting is not too bright – which washes out the picture and 3D imaging – but also make sure that it’s not too dim either, with all of the lights turned off, because that definitely causes eye strain from excessive contrast in the visual field. It’s best to have some subdued illumination surrounding the TV. Consider repositioning, dimming or turning off room lights that reflect off the screen. If you have Active Shutter Glasses consider turning off any fluorescent lights or replacing them with LED or incandescent bulbs.

 

Adjustments:  be proactive and make a few adjustments to the TV Menu settings. The most important are Backlight Brightness and Color. Set them appropriately for your viewing conditions and comfort:  not too high or too low, just right… Start off by significantly lowering the Backlight Brightness so it is too dim, then slowly raise it until it feels just right. TVs are frequently set too bright for night viewing, which causes eye strain. Excessively strong color can also cause eye strain, consider adjusting it as well for maximum comfort.

 

3D Viewing Issues:

When watching 3D TV some of the above issues become more important, and there are also a few additional considerations:

 

1. Don’t sit too close to the TV – a minimum of 6 to 8 feet. Move back if you sense eye strain or fatigue. Proper eye height and optimum viewing angles are especially important for viewing 3D. A tilt mount is essential if you have put the TV high up, like over a fireplace.

 

2. Don’t watch 3D in the dark. Make sure there is sufficient ambient light so that you can focus on the bezel or frame of the TV in order to make it easy for your eyes to establish the proper focal distance for the on-screen 3D images.

 

3. Avoid staring at out of focus objects and content because your eyes will automatically try to bring them into focus, and can’t, which causes eye strain.

 

4. Limit the amount of extreme 3D and Out of the Screen effects, which often lead to eye strain. Consider sitting further back from the TV if there is a lot of it.

 

5. Because of the way the brain processes 3D information, viewers at different viewing angles will see somewhat different perspective views of the same 3D image. The effect can be quite large when a scene has significant depth.

 

6. Don’t combine large vertical viewing angles with off center horizontal viewing because their combined Crosstalk and perspective effects are cumulative.

 

Recommendations for 3D Producers

The biggest issue for 3D production is using the same cameras and camera techniques for combined 2D and 3D shooting. For 3D try not to have anything out of focus anywhere in the picture – in particular don’t use focus and limited depth of field to highlight the main object of attention the way it is normally done with 2D. It’s very important to maximize the depth of field and keep everything in focus at all times for 3D content.

 

People have very different tolerance levels for the amount of extreme 3D and Out of the Screen effects they can watch without suffering eye strain and fatigue. For 3D Blu-ray content give viewers a setup option to choose the amount and degree of the effects that they would like to see and then implement it with Seamless Branching during playback.

 

Article Series Link:  Display Technology Shoot-Out Article Series Overview and Home Page

 

Acknowledgements

Special thanks to Nick Stam and Andrew Fear of NVIDIA and Jim Taylor and Tom Kopin of Kramer Electronics for their help and providing hardware, software and support.

 

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.info@displaymate.com.

 

About DisplayMate Technologies

DisplayMate Technologies specializes in advanced mathematical display technology optimization and precision analytical scientific display diagnostics and calibration to deliver outstanding image and picture quality and accuracy using our DisplayMate Display Optimization Technology. Our advanced scientific optimizations can make lower cost panels look as good or better than more expensive higher performance displays. See DisplayMate’s Outstanding Industry Recognition, Reviews and Awards. 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.

 

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