Skip to main content

Primer: The Principles Of 3D Video And Blu-ray 3D

Other Considerations


Because they block alternate pixels, rows, or frames of video from each eye (depending on the type of 3D display you have chosen), less than half the light from a 3D display system reaches your eyes. To minimize crosstalk on frame sequential display systems, active shutter glasses block both eyes during the transition period between the display of each video frame. For all of these reasons, it is helpful to choose a 3D display with high brightness levels.

It is also important to avoid any reflections on the screen of your TV or display, as these reflections will be seen at a fixed depth (the distance from your eye to the display), making it a bit harder for your eyes to naturally focus on whatever you are interested in.

Due to both concerns, (brightness and reflections) you will find that 3D video is best viewed in a dark room.

Accommodation Disparity

Although objects may appear to be in front of or behind the display, they are not really there. Because the image is really coming from a flat screen, to see the 3D video clearly, the muscles in your eyes must keep your eye lens focused to the distance of the screen. The fact that the 3D video is really only in focus on a flat plane creates a disparity between one visual cue (accommodation) and the other visual cues. 

When your eyes try to focus on 3D objects that appear to be close to you, your eyes will naturally converge inward while trying to accommodate for viewing a nearby object. Unlike the real world, all objects in a 3D video will only be in focus on the display. If you try to focus on objects that appear to be right in front of your nose, you will be disappointed, as you instead lose focus.

Fortunately, it seems that most people are able to adjust to this disparity without much difficulty, letting them relax and enjoy a 3D video without losing focus.

Blur Disparity

In the real world, our eyes focus on the objects at which we are looking. Objects that are nearer or farther appear out of focus. Because a 3D video is presented on a flat screen, the blur gradient that we experience in the real world will not be seen in a 3D video. If the 3D video is shot with a wide depth of field, the majority of the scene will be in focus, allowing the audience to see any part of the scene clearly when they focus on the screen.

If the director or cinematographer chooses to use a narrow depth of field, scenes may be shot with the subject in focus and other areas out of focus. While this technique can approximate the blur gradient we experience in the real world, it has the drawback of causing objects that we would normally be able to focus on to be out of focus, and impossible to focus on.

Blur disparity is an unavoidable issue, regardless of how a 3D video is shot or rendered. Studies have suggested that blur disparity and accommodation disparity tend to provide a cue to the brain that although it is seeing a stereoscopic view of a three-dimensional scene (real or computer-generated), the actual 3D video presentation is on a flat screen.

Eye Strain

We naturally view our world in 3D, and so a good 3D production makes it easy to suspend the disbelief that we are not actually “on scene,” live and in-person. However, the viewer will naturally try to focus to different distances, depending on the apparent distance of subjects and scenery in the 3D video. When you not only scan your eyes from side to side, but focus in and out, your eye muscles get a bigger workout than you would get from watching a video in 2D. Once you are able to adjust to the brave new world of 3D video, you will find yourself relaxing and enjoying, instead of trying to actively focus on objects near and far. 

Motion Sickness

Motion sickness is normally caused by a disagreement in your brain between what you see and the motion that you feel (by your inner ear, which gives you your sense of balance). Motion sickness can also be caused by a disagreement within the visual system of your brain. If a 3D video is shot, displayed, or viewed poorly, the 3D depth perception of the objects in the scene may conflict with the 2D depth information that we perceive. These conflicts can cause the viewer to suffer similar symptoms to common motion sickness (fatigue, headache, dizziness, or in the worst case, nausea). 

3D producers know how to minimize the potential for problems by:

  • keeping subjects in the 3D comfort zone, at roughly the distance of the convergence point of the camera (at least most of the time)
  • avoiding focusing on objects that are extremely close to the camera (your eye will try to focus on the object as it if is close to you, when your eye needs to focus to the distance of the display)
  • avoiding zooming in and out (which changes the scale of the 3D space)
  • avoiding excessive camera motion (for example, flying through a jungle; the audience has suspended the disbelief that they are watching a movie, and now the subconscious part of their brains are more prone to be concerned when their eyes are telling them that they are flying through the jungle but the sense of balance from their ears is telling them that they are sitting still)
  • keeping near subjects away from the edge of the frame (where the picture for one eye could leave the frame)
  • being sure that all content is 3D (producers cannot use flat 2D backgrounds or effects in a 3D production)
  • minimizing the use of a narrow depth of field (causing parts of the scene to be out of focus – causing problems for viewers who attempt to focus on these objects)

Fortunately, experienced 3D producers know how to avoid these problems. 

Consumers can minimize the potential for problems by:

  • choosing a high-quality 3D display and 3D glasses solution (minimizing ghost images caused by crosstalk)
  • minimizing reflections on their TV or display (reflections are 2D)
  • viewing 3D content from the center of the direction that the display is facing (or from the center of a 3D theater – keeping the relative distance of all parts of the scene centered and in proportion)
  • JohnnyLucky
    Very informative primer. Lots of information that was easy to undertsand.

    Unfortunately I am one of those who recently purchased a new TV. It will be quite some time before I upgrade.
  • TheGreatGrapeApe
    Nice article, but I think there's a few issues with regards to the overall balance of the information being put forth.

    I understand the author's preference for shutter glasses (especially since it's a certain product's preferred method of choice) even if I don't share it, the major limitation is having to buy a pair for all your friends coming over, which gets impractical until they are more commonplace.

    Also polarized solutions are not limited in resolution if they are set-up beyond just the example provided in this article (like they do in the theatre with dual projectors ) and may have an improving single source future with 2K and 4K displays on the horizon. It's a question of preference, but it seems like the full story wasn't explored on that subject.

    Now on to a pet peeve: I love the part about "While set-top Blu-ray players will need to be replaced, PC-based Blu-ray player software can be upgraded." as a subtle product benefit plug.

    Unless it's a free upgrade, you are still replacing the software, not upgrading it (it's not a plug-in), and you're likely forking out nearly the same amount of money for the 1/100th of the cost to produce that software update, so it's not like it's a major advantage. Especially when upgrading requires a FULL upgrade to the most expensive model Power DVD (version #) Ultra 3D, and I can't simply add it to my existing PowerDVD bundles thus potentially changing my backwards compatibility (Ultra 9 already removed my HD-DVD support from Ultra 7 that I upgraded on my LG HD-DVD/BR burner

    , until then it's $99 (or $94.95 for loyal saps) vs $150-200, plus with the set-top route now I have a second BR-/DVD player for another room or to give to a friend (the BR software on its own is useless to give to someone else without a drive), and that's not even compared to the free PS3 upgrade.

    Also can someone explain this statement;
    "Blu-ray 3D video decoding solutions can be expected for ATI Radeon 5000-series graphics in the future."

    Didn't Cyberlink already show their BR-3D solution on ATi hardware last year? So what's the issue?

    Also why is it limited to "GeForce 300M-series mobile graphics" when often the core is the same a previous generation 200M series (example GTS 350M / 250M )?

    And this section "Full-quality 120 Hz frame-sequential 3D video (such as Blu-ray 3D) is only supported through a High Speed
    HDMI cable to a HDMI 1.4-compliant TV. " seems to miss the DVI dual-link to monitor option currently being used for 3D on PCs, and also the dual 1.3 input monitors/TVs.

    A nice little article for people unfamiliar with 3D, but there's a subtle under-current of product preference/placement in it, and far too many generalities with little supporting information. :??:
  • hixbot
    well done. I would of liked more detail on the hdmi 1.4 spec, specifically framepacking and the mandatory standards (no mandatory standard for 1080p60 framepacking).
    also some info on AVRs and how a 1.3 hdmi AVR might pass on 3d video and still decode bitstream audio, or not - do we need 1.4 hdmi AVRs to decode audio from a 1.4 source? we shouldn't need 1.4 receivers since the audio standards haven't change, but I'm understanding that in fact we do neeed new receivers. :/
  • hixbot
    double post. good article.
  • ArgleBargle
    Unfortunately for people with heavy vision impairment (astigmatism, etc.) which require corrective lenses, such 3D technology is out of their reach for the time being, or at least next to useless. Until some enterprising company comes out with 3D "goggles", people who wear corrective lenses might as well save their money.
  • boletus
    3D is cool, and high definition video is cool. But Sony's moving target of a BD standard is not cool, and Cyberlink's bait and switch tactics are not cool (unless you have bundles of money you can throw at them every 6-12 months). I sent back my BD disk drive (retail, with Cyberlink software) for a refund after finding out that I would have to shell out another $60-100 just so I could watch a two-year old movie. As far as I'm concerned, high definition DVD video is dead until some more open standards and reliable software emerge.
  • cangelini

    This piece is a prelude to tomorrow's coverage, by Don, of Blu-ray 3D on a notebook and a desktop. Perhaps that one will answer any of the questions you were left with here?

    As for AMD, Tom and I went back and forth on this piece, and we agreed that it was critical to get AMD's feedback on Blu-ray 3D readiness. The fact of the matter is that it isn't ready to discuss the technology. It's behind.

    The mention of dual-link DVI was in the first revision of this piece and removed in a subsequent iteration. I've asked the author for additional clarification there and should have an answer shortly.
  • cangelini
    So it turns out there were two sections on this and one was cut accidentally. Should be good to go now, though--dual-link DVI is discussed with PC displays!
  • cleeve
    TheGreatGrapeApeAlso can someone explain this statement;"Blu-ray 3D video decoding solutions can be expected for ATI Radeon 5000-series graphics in the future."Didn't Cyberlink already show their BR-3D solution on ATi hardware last year? So what's the issue?
    It turns out the demo (I think it was at CES?) only used CPU decoding over an ATI graphics card; the Radeon did no software decoding.

    The Cyberlink rep tells me that Blu-ray 3D software decoding is extremely CPU-dependant and might even require a quad-core CPU. He said all four threads were being stressed under software decoding, not sure what quad-core CPU they were using though.

    Definitely something I'd like to test out in the future...
  • Alvin Smith
    This was a very informative and well written article BUT, I chose to skip to the last two pages ... Because ...

    These implementations, while ever more impressive, are still being threshed out. Because of possible physiological side effects, I think I will NOT be a first adopter, with this (particular) tech (3D).

    Anyone ever watch that movie "THE JERK", with STEVE MARTIN ??

    = Opti-Grab =

    ... I can see all these class-action suits by parents of cross-eyed gamers ... hope not, tho ... I *AM* very much looking forward to the fully refined "end game", for 3D ...

    Additionally, the very best desktop workstations are only just now catching up to standard (uncompressed) HD resolution ingest and edit/render ... since that bandwidth IS shared, between both eyes, this may be a non-issue.

    I will let the kiddies and 1st adopters take-on all those risks and costs.

    Please let me know when it is all "fully baked" and field tested!

    = Alvin = (not to mention "affordable").