Film-Tech Forum ARCHIVE: Can Sony show 3D without RealD?

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Posted by Peter Castle (Member # 1997) on 06-15-2009, 04:58 AM:

One of the problems with polarised 3D is the drop off in brightness as the viewer's angle to the screen increases, due to the silver screen's very directional reflection.
That is why the other methods (shutter glasses and Dolby 3D) are the only solution for wide cinemas.

Can you use Sony's 4K projectors with any of the other methods?
Certainly Sony seem to have got into bed with RealD to the detriment of sales to a lot of cinemas where silver screens are useless.

Posted by Julio Roberto (Member # 4976) on 06-15-2009, 09:38 AM:

Of course Sony could use any other system instead of polarized light to do 3D.

They could, i.e., use shutter glasses, BUT their refresh rate (60hz against DLP 144hz) is way too low for any sensible application. It would flicker too much.

Then, you could just use static infitec (Dolby) filters on each of a dual lens assembly, instead of the polarizing ones being used in their current solution. This would make the system equivalent to Dolby 3D, except it wouldn't have some of the drawbacks like flicker (temporal disparities) or problems associated with the transport of 48fps 12bits 4:4:4 signals.

But it would be a bad move as the Sony projector already outputs polarized light whether in 2D or in 3D, so when you use a polarization system for 3D you can actually use a large percentage of the available light "as is" (i.e. no huge reduction in brightness).

If you were to put static Infitec (Dolby) filters in front, which don't benefit from the light being already polarized, you would get your usual huge drop in brightness which would render the Sony's only useable for really small screens.

So polarization makes the most sense for the Sony.

Polarization systems don't "inherently" have problems with illumination uniformity at severe angles of view, but in practical terms they do, because of the "requirement" of a silver screen. What I mean is that one could manufacture a screen that preserved polarization sufficiently well while offering a low gain and, thus, a "perfect" illumination uniformity at any angle. But in practical terms, no such screens are manufactured for cinemas. This would be the closest thing:

http://www.da-lite.com/whats_hot/index.php?wID=176

quote:
Other major benefits of 3D Virtual Grey include a gain of 1.3, viewing half-angles of 11º

Although it only has a half-angle of 11º, the gain is only 1.3, so you could figure a sensible illumination uniformity that "only" decreases up to 60% from best-to-worst possition (typically ~20%), instead of the usual silver screen which can range upwards of 300% (typicially ~120%).

Typically we get:
-Silver screens: gains of 2.2 to 2.4, half-angles vary up to 24º
-Screens usually used for Dolby 3D: gains of 1.6 to 2.2, half angles vary up to 24º
-This screen we are talking about: gain of 1.3, half angle of 11º

If you made such a screen with an additional lenticular emboss and curved it a bit, you would get a screen for polarized 3D with even much (much) better uniformity than those typically used for Dolby 3D.

But yeah, in practical terms, today, from the available solutions marketed to cinemas, polarized systems suffer the use of very high gain screens which means that all the "extra" light you gain in the center viewing position, say "double" that of white matte screen, you lose when you are sitting at a ~45º from the center (say half of that of a matte screen).