A 360° View of 3D

September 21, 2011

The time has come at last to splash out on one of the new fangled plasma or LED TV sets.

However, my ancient 28" Panasonic QuintrixF box with the excellent Tau flat-screen, having done 10 years of faithful service (albeit with a couple of repairs during that time), has started to show tell-tale signs of impending failure – the Dolby Surround circuitry lost the centre channel a year ago and the picture does an occasional wobble at the top.

I would get it repaired but I’ve a feeling that finding parts might be problematic now and, besides, there are some excellent new TVs on the market (or so I’m told) that should do the job AND they’re 3D capable too.

I’ve put off buying a new TV over the last few years, even when true 1080p HD came out as the picture quality on these sets, even with all their HD-ness, just wasn’t up to the QuintrixF Tau screen. When it came to watching standard definition (SD) video on them, they couldn’t hold a candle to my Panasonic CRT TV.

But it’s time to look around.  I’m a bit of sceptic when it comes to the marketing-hype of consumer electronics and like to see the products in real-life use.

The up-market screens from pretty much all the major manufacturers are very capable now, though I’d argue that their HD picture quality is no better to my current TV, and are much improved in up-scaling SD signals so as to avoid that apparently blurry image especially prevalent on low-bitrate channels.

Buying such an up-market screen generally means getting a 3D-capable set as the manufacturers pair their best panels with the best electronics.  I imagine that this seriously over-weights the statistics of people "buying into" 3D technology over the last year so.

With this in mind, I’ve spent the last few months pestering friends and relatives who did take the plunge last Christmas and bought a 3D capable set back then.  So now, having now watched quite a bit of 3D footage, courtesy of their hospitality, I’ve made some observations of the medium.

Apart from the technical issues, such as faded colours, image cross-talk, the physical restrictions of passive 3D glasses and the costs of active 3D glasses that people often talk about, there are four perceptual problems of 3D that I’ve noticed.  This is just my opinion, but it’s my blog, so here they are:

Lack of Near-Field Parallax
I’m not sure if this is what it is really called but it seems quite descriptive of the effect.  When an object is in the foreground and is apparently close to the viewer, if that viewer moves their head they’d expect the object to move in relation to the background, revealing new areas and obscuring others.  Obviously as the picture is actually flat and only presents a static 3D view this doesn’t happen and spoils the immersive experience.

This isn’t such a problem with more distant objects as a viewer expects much less parallax to occur between such an object and the background.  The best way around this seems to sit still and watch TV as if you’re in the cinema – maybe some people do this but, personally, I don’t.

Assuming an Infinite Depth of Field
In standard 2D content the director typically denotes the main subject of the scene by focusing on them with a shallow depth of field. The background appears deliberately out of focus but that OK as it’s pretty much how our eyes work.

In 3D content there seems to be a preference to demonstrate its 3D nature by having an infinite depth of field with everything in focus, even when a "special" 3D effect is used, as is the wont in the traditional realm of 3D horror films.  This practice makes the next two effects seem worse than they might otherwise be.

Billboarding
I don’t believe that this is a correct term but it’s quite descriptive of the apparent effect.  In short, current 3D technologies don’t seem to capable of providing a completely smooth depth transition between objects in a scene.  I don’t know if this is a feature of the cameras or the TVs.

This shortcoming leads to "billboarding" – in that it appears that a 2D picture of a 3D scene has been pasted onto a billboard which is then set at a distance into the scene. This technique used in video game development to reduce the computational complexity in rendering.

The scene is seen to be composed of a set of these "planes" rather than being smoothly graduated.  In worst cases, this effect is even seen on single objects. For example, on one demo the viewer was taken across the Pont Sant’Angelo in Rome (which I recommend visiting sometime) and there were close ups on the 17C angelic statues.

Unfortunately, although the picture was excellent, the statues appeared dislocated. Where a hand was pointing “out” of the screen it was disjointed from the forearm, which was on another "plane", and this extended to the shoulder, wings, etc. It was as if it was a Channel 4 ident with pieces of stone suspended on invisible wires and visible as a solid body only when viewed from a specific angle.

Focal Distance Adjustment
This seems to sort of related to the "Infinite Depth of Field" issue I’ve mentioned above.  In order to "believe" a 3D scene, it seems that my eyes have to be fooled into assuming that the objects are a certain distance away.  When the scene shifts whereby the "focus" is now apparently at a different distance but remains in focus without my eyes having to re-adjust, it seems wrong. At best this just destroys the illusion of 3D until I "lock in" again but, at worst, it makes me feel a little seasick!

So what do I believe this means for 3D TV?

The technology will continue to improve so the technical concerns will probably be consigned to history within the next few generations of the systems themselves.

The limitations of physical equipment will be solved as, I imagine, should the "billboarding" effect described above – unless this is actually some form of physiological limitation of human cognitive processing.

The issue with lack of near field parallax will probably drive the adoption of VERY large 60”+ screens that can be placed farther away from the viewer so that the problem is just less pronounced.  Unless the TV can generate a private 3D image for each viewer and use some form of individual eye tracking I don’t see how else this might be tackled.

The other issues are really a matter of direction style.  The modern way of shooting 2D TV seems to to use close in cameras with rapidly changing viewpoints in order to engage the viewer and make them feel like they’re actually part of the action.  What works well for 2D simply doesn’t work for 3D.  The rapidly changing perspective just leads to disorientation and destroys the immersive 3D experience.

I believe that, for 3D, viewers need to be treated more like a theatre audience as passive onlookers onto a scene.  Viewpoints need to be established and held in order for the audience to “lock in” to the scene’s perspective.  This means that the 2D version of a film won’t just be a single-eye image of a 3D film but, for a large part, a differently shot piece of work.  Obviously this will push up production costs.  I don’t like to think that we’ll be seeing 2D movies going the same way as black and white movies and only being shot as art nouveau retro pieces.

In short, 3D holds a lot of promise, especially in the gaming market where the scene is being generated on the fly, but for general viewing I’m really not convinced that there’s a great need at the moment (sport may be an exception though) until the content production industry works out how to handle the artistic differences between 2D and 3D in order to get the most from both mediums.  There is some fantastic 3D content out there but not enough to warrant buying a 3D set specifically to see it.

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