3D Crosstalk

When I went to the Sony 3D TV launch a couple of months ago, and to the Panasonic 3D TV launch a couple of weeks ago, both the spruikers of the new 3D technology highlighted the superiority of their system for eliminating crosstalk. At the time, I was a bit dismissive. Suppliers always talk about how their solutions to particular problems are better than the competition’s,┬ábut in most cases the competing techs tend to converge towards similar performance levels.

But it has now become apparent to me that avoiding crosstalk in 3D TV pictures is not just important. It is vital.

So what is 3D crosstalk?

The essence of all currently practical 3D video systems is to present different images to the left and right eye. This can be done by carefully colouring the two images and displaying them at the same time, and using coloured filters to separate out the two for the two eyes. Or the same can be done using differently orientated polarisation for the two eyes.

For consumer TVs, though, the various brands have chosen shutter glasses. That means that both the left and right images are not shown at the same time. They are shown one after the other, alternating between the two at least 50 times per second in PAL systems, 60 times in NTSC. The LCD shutters in the glasses stop each eye from seeing the other eye’s image.

If you look at the picture without using the glasses, this is what you see:

This is a scene (on pause, but this doesn’t effect the alternate imaging which creates the 3D effect) from a demo disc. The disc has four short clips from the 3D version of Monsters vs Aliens, repeated eleven times for a total duration of over two hours. It is labelled for shop use only.

Now it it’s pretty obvious that there are two slightly different images overlaid in this. Remember, one eye is supposed to see only one of these, and the other eye is supposed to see only the other. The reason we can see both is that I made my camera expose this shot with a slow shutter speed so it captured both the left and right, um, fields. I shall call them fields for the moment.

Now I have on my test bench right now a 3D TV and a 3D Blu-ray player, and the disc from which this shot was taken. I shall not identify the brand because the result is very disappointing, and it could be that the devices I have aren’t operating properly. I shall chase that down tomorrow.

So here’s the same shot, but with the camera taking the photo through the right lens of the shutter glasses:

Now, you will notice that the image has firmed up considerably, with it much easier to make out the structure of the bridge tower behind the girl, and see that each set of suspension cables consists of two, not three, cables.

But you will also see that there is a ghost to the left of those features. That’s because there is. I’m hoping this TV is defective, because that is major league crosstalk, or leakage, from one eye to the other (the left eye image has the same problem, but with the relative strength of the fields reversed).

The photo fairly represents what this actually looks like. There was some 3D effect, but it took an effort of will to look for it. Instead, the ghosting (all the way through, although not as obvious in lower contrast scenes) distracted my eyes, made the 3D effect quite unconvincing, and make the video difficult to watch because my eyes felt as though they were blurring the image.

To finish, here is a closer view of the bridge tower, with the both-eye-view on the left, and the right-eye-view on the right, complete with marked crosstalk or ghosting from the left eye view:

If this turns out to be defective equipment, then I shall actually be kind of happy that I’ve had this opportunity to learn how important crosstalk can be.

If it isn’t defective, then this equipment cannot be recommended.

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11 Responses to 3D Crosstalk

  1. Coby says:

    Hi Stephen,

    Not much is being tested regarding new technology it seems everyone gets cuaght up with the flashy lights but forgets the reality or details sometimes.. hats off to actually TESTING a product.

    I would be interested to see other brands / models tested to see if they had similar results.

    You also mention you have seen another two brands – did they also delvier the amount of crosstalk you have posted?

    Thanks

  2. Stephen Dawson says:

    I tended to just go ooh! aah! like everyone else at the launches. I have no recollection of any crosstalk, but I shall reserve judgement until I get actual review products from those brands in my office.

  3. Peter says:

    Hi Steve

    Talking about 3D.

    When I purchased my copy of Coraline (great movie) from the States it came with the option to play it in either 2D or 3D, and they included the 3D glasses as well. Can you explain how the 3D thing works when I’m not using a 3D plasma or LCD screen (I actually own a projector with 110 inch screen) or a 3D Blu-ray player.

    Regards
    Peter

  4. Stephen Dawson says:

    Australian version of Coraline is the same. This uses coloured filters to separate the image for the two eyes. The three main systems for stereoscopic 3D are coloured filters (you will notice that the colour palette is very constrained in the 3D version for this reason), polarising (light polarised in one direction admitted to one eye, and a different direction for the other eye – commonly used in cinemas now), and sequential (LCD shutter glasses).

  5. Damir says:

    It is nothing wrong with TVs. All of them (I saw Samsung, Panasonic and Sony) have some crosstalk. However, Panasonic had the lowest crosstalk among tested sets. You can see crosstalk on contrast subjects (e.g. bright subject on a dark background) which are placed far behind the screen level (far behind stereoscopic window or deeply “inside the picture”).

  6. pablo says:

    After lots of test Sony Samsung & Panasonic have crosstalk. comparatively Panasonic is low. I want 100% cross talk free 3d tv. Now I have to go for for other companies like Tossiba, LG.

  7. First gen LG was amongst the worst. The new LG with passive glasses seems pretty good, except it is half resolution on 3D. New Samsung LCD is much, much better than last years.

  8. Dave Hanson says:

    I have a almost Cross Talk Free, LGLW5600.

    cross talk is 4x less likely to happen on Cinema 3D sets and they are also flicker free.

    In case you were wondering my TV is the LW6500 its 55″ and came with 4 glasses when I bought it. Which was really nice for my family
    Active TV is so crappy with all that flicker and cross talk. I am really happy with my TV and would recommend any one to go out and get one as well it is the best 3D TV in my opinion.

  9. Ryan Sandford says:

    That is a lie regarding the half resolution. The brain combines the image for full HD def. Anyone with a set of eyes working properley can see this and if they compare. See this link for a detail study on passive ve active – http://www.displaymate.com/3D_TV_ShootOut_1.htm#Recommendations

    I just bought a Soniq 42 inch for $399, which is actually sourced technolgy wise from LG. It is awesome and I highly reccomend it to anyone.

  10. Welcome Ryan. Two things. First, it is impolite to visit someone’s blog and call them a liar. I shall assume that you are not aware that a lie is an intentional falsehood, and that you merely meant that I was in error.

    As to that point, I have just produced a lengthy post, here.

  11. Bob Dobbs says:

    As far as I know (for consumers), there’s one very cheap, another very expensive — method to have true, crosstalk-free 3D viewing — without shuttering or polarization.
    The cheapest method requires a pair of prism glasses http://www.nvp3d.com/en/prism-glasses or Stereoscope http://www.nvp3d.com/en/Stereoscope1 to converge Side-by-Side (Left/Right) images from a single display (e.g., a tablet computer … p.s. if your 3D-SBS content is 16:9 then you’ll want to force a playback aspect ratio of 32:9 for this). Google recently announced Google Cardboard cardboard.withgoogle.com as the ultimate cheapest (hence, “Cardboard”) 3D viewer (for Google Nexus 4 and 5, Samsung Galaxy Nexus, Samsung Galaxy S4 and S5, Motorola Moto X smartphones). Meanwhile, awaiting the release of the Oculus Rift, http://www.oculus.com, Samsung has announced “Gear VR Innovator Edition, a new mobile virtual reality headset using the Galaxy Note 4, created by Samsung and powered by Oculus.”
    Alas, the most expensive method requires discrete, high-definition displays with higher-quality optics, such as the Sony Personal 3D Viewer (HMZ-T3W) discover.store.sony.com/personal-3d-viewer around $1K USD (ouch).
    However, I’m still im/patiently waiting for the availability and affordability of Dolby 3D “glasses-free 3D for TVs, PCs, and portable devices” http://www.dolby.com/us/en/technologies/dolby-3d.html

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