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The Renaissance of 3D:
How the New 3D Technologies Work

Bill Livolsi, February 5, 2010

Polarizer Method

Light polarizing systems are used in commercial cinema and other high-end applications. These methods provide a high-quality 3D experience in commercial cinemas, made even better thanks to the prevalence of digital projectors. In a polarizer system, light from the projector or projectors passes through a polarizing filter which makes all the light waves oscillate in the same direction. Special filters on the viewer's glasses allow only the light meant for that eye to pass through. If you have ever seen a set of Venetian blinds, you already understand the concept--from certain angles you can see through the window clearly while from other angles your view is obscured. The use of different polarization for each eye allows for two discrete images to be projected, one for each eye, which creates the impression of depth.

There are two different polarizer-based systems currently used for commercial 3D projection. One version uses two projectors, each with its own polarizing filter, to project the left- and right-eye images. This system is used in IMAX 3D presentations. The other system, known as RealD, uses one projector and a fast-switching single polarizer to accomplish the same thing. This system flips between left-eye and right-eye images very quickly and the polarizing filter switches between clockwise and counterclockwise polarization in time with these switches. Again, polarized glasses allow the viewer's eyes to see only the information intended for them.

Advantages of Polarized 3D

Color. Compared to anaglyph systems, color is more accurate when using a polarized system. While there is some light lost because of the glasses, colors are closer to their original values. It is also easier to color-correct material used in a polarized system since the lenses have very little color to them. Flesh tones in particular look more realistic and believable when viewed on a polarized system.

Passive glasses. Like anaglyph 3D, polarized 3D uses passive glasses which are inexpensive and contain no electronic parts. Unlike anaglyph, polarized glasses' frames are usually made of plastic which makes them more durable and reusable than their paper-framed counterparts.

Cross-talk. Polarized systems have a lower incidence of cross-talk than anaglyph systems. Due to the properties of polarized light, it is almost impossible for the left eye's image to make its way into the right eye or vice versa. Systems using left-right polarization such as IMAX can lose the 3-D effect if you tilt your head too far to either side, but unless you are sleeping on your neighbor's shoulder, this should not be a problem.

Disadvantages of Polarized 3D

Light loss. In all single-projector 3D systems there is a significant reduction in luminance when compared to a 2D system. For the non-physicists in the audience, luminance refers to the light reflected from a surface (in this case, the screen) at a given angle (in this case, towards your eyes). This is not the same as illuminance, which is a measure of the light striking a surface per unit of area, typically measured in lumens per square meter and posted in all of our projector reviews.

In all systems except anaglyph, this loss is caused by the rapid switching necessary to display discrete left and right eye images. At any given moment while watching a 3D movie, one eye sees a projected image while the other eye sees nothing at all. As such, each eye only sees half of the light reflected from the screen, resulting in a luminance reduction of at least 50% right off the bat. I say "at least" because polarizers and glasses are not perfectly efficient. Polarization by its very nature only allows a portion of the projector's total light to reach the screen. There is some further light lost due to the glasses. The end result is a picture that appears much less bright than a 2D film from the same projector.

This is actually one of the chief advantages of using a two-projector system. Each eye gets the benefit of the full light output of one projector, though light loss due to polarization and glasses still apply. The end result is a much brighter picture, all else being equal. That last part is important because all else is not likely to be equal. The most widespread commercial implementation of a two-projector system is IMAX, which also uses a much larger screen than most RealD theaters. The projectors used can vary in their lumen output. Polarizing plates can vary in their efficiencies, as can glasses. There are too many variables to make any definitive judgement about which system is "better," but each has its advantages.

Expensive. While the glasses themselves are inexpensive, the rest of the system is not. It requires at least one high-end digital projector paired with a special processing device to manage synchronization, at least one polarizing filter, and a silver screen (traditional white screens cannot hold polarity). Two-projector systems obviously require two projectors and two polarizers.

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Contents: What is 3D Anaglyph Polarizers Interference Filter
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Comments (19) Post a Comment
Currious Posted Feb 5, 2010 5:41 PM PST
So what about glasses-less 3D TVs?

Some companies claim they have that techno in store, from a flat screen.

One easy way to generate 3D that has been done, is to use a fast rotating screen, and as it turns display different pixels for that 3D position.
DD HT Lover Posted Feb 6, 2010 7:00 AM PST
Another fantastic article. Thanks for keeping us ahead of the curve again.
Paul Posted Feb 6, 2010 12:34 PM PST
When special glasses are no longer required, I'll be interested.
Matthieu Posted Feb 8, 2010 6:10 AM PST
Wow you did your homework VERY well. I'm into the 3D photogrphy for a long time and still I learned some things about tech stuff from yur review.
MREUM Posted Feb 10, 2010 9:31 AM PST
I still think 3D is a fad, just like before. People will tire of it, particularly if the 3D films are no better than what has already been produced. Until a system emerges that does not need glasses I do not see it being anymore than a novelty, although the adolescent gaming crowd will probably like it.
willdao Posted Feb 11, 2010 3:03 PM PST
Bill,

Very nice, comprehensive article!

Will
Wyatt Posted Feb 12, 2010 11:35 AM PST
As someone who has been working on a 3D film for the past year now and has experienced looking at the same material with all technologies (except for Interference3D), I can tell you that a good pair of shutter glasses is the best way to go.

I am sensitive to 3D cross-talk and the shutter glasses eliminate this completely for a crisper / cleaner looking image. Another advantage is that you do not have to keep your head on a level plane, so if you wanted to lay down on the couch with your head cocked sideway, shutter glasses would still work as intended. Polarized glasses do not stand up well to this.

Hopefully shutter glasses win the format war and will be mass produced making them much more affordable than they currently are.
libair Posted Feb 15, 2010 1:09 AM PST
well i think that it will take a long period before we see broadcasting in 3d although in korea this technology is here experimentally of course!!so its difficult for me who bought an hdtv this summer to participate in this even if this is 2-3 years ahead!!without the display that is capable of 3d you can only dream of 3d movies!does anyone know if there is a possibility for a top video box lets say to convert hdtv to 3d ready???of course not the 60hz but the 120hz or 200 hz ones...would that be possible!!from the other side here in grece where i live we will have the h.264 in a couple of months so i think the 3d broadcating about a century ahead!!!
Roy Posted Feb 16, 2010 11:56 AM PST
Very informative article. Thanks!

Because "3D Vision" glasses are another $200 on top of the cost of the projector, is it possible ProjectorCentral might consider a combo/package/bundle price where a person could buy say the new ViewSonic 3D projector + Nividia 3D Vision for a package price of around $500?
Jeff M. Posted Feb 22, 2010 9:41 PM PST
I don't know about the rest of you but I am ALL about 3D! If anyone on here could help me, my email is kraftmacincheese@yahoo.com I have been scowering reviews and the like in the search for a 3D projector with the crispest video that 3D projectors can offer. I am going to be throwing a distance of about 10 feet and trying to fill up a 110" screen as much as possible in a 16:9 or similar ratio. I have my eyes on the Epson 8500ub because of the awesome 200,000:1 contrast however it does not have 3D capabilities. So can anyone help me with this. I am trying to find the absolute BEST 3D projector on the market that I can get for around 3000 or so. However I am afraid that the image won't be crisp for movies and games like on one that has a contrast such as the Epson. I am a noob to projection and all of that but am computer literate so you don't have to speak slowly lol :P Thanks everyone.

Jeff
Stunko Posted Apr 8, 2010 9:17 PM PST
The current round of 3D hype will be dead inside of 24 to 36 months.... and will be resurrected some time later again... and again... and again.
Vincent Posted Apr 12, 2010 8:41 PM PST
In the 3D race, seems like the LCD/Plasma TVs are a little faster than projectors. Please correct me if I am wrong. Some of the TVs such as Samsung already supports 3D BlueRay directly (i.e. supports HDMI 1.4 format). Most data/home projectors only support HDMI 1.3 (1080P but not 3D). HDMI 1.4 is a relatively new standard.

Second problem is that it seems that only DLP projectors can support 3D projection. LCD based projectors cannot refresh at 120Hz. So quite a number of brands of projectors will not be able to get into the bandwagon so quickly.

For those looking for 3D experience using a projector and at 1080p, I guess the projectors will only be available some time later this year.
Richard Posted Apr 25, 2010 10:32 AM PST
I'm curious about one other thing. Isn't the end user dependent on the kind of coding that appears on, for instance, a Blu-Ray disk? Will these disks contain all the various encoding schemes, or what? Will I have to shop carefully, noting the kind of technology present on a specific disk before I buy it? If so, the media producers can quickly determine what standards will be weeded out, and buying anything now is premature. Just like VHS and Betamax all over again.
Bob Posted May 29, 2010 7:51 AM PST
So, if my projector refreshes at 120 Hz already, what is the prognosis for an interface box to decode Blu-ray 3D signals interlaced at 60 Hz for left and right eyes and providing the synchronization signal for the shutter glasses?
mdf Posted Jun 2, 2010 10:03 AM PST
Glasses-less 3D will never happen with current displays or projectors. In order for 3D to work, your right eye and your left eye have to see different images. If you shift a few inches to the right on your couch, how could your left eye not see what your right eye had been seeing? Until there are non-static holographic displays (there aren't and no one is working on them) the laws of physics make a glassesless 3D technology completely impossible.
Yllon Posted Jun 20, 2010 4:59 AM PST
This is not exactly true. Hitachi as come up with a way for you to see 3D with out the glasses. It is called parallax viewing. While this format is a year or two away and is only available in flat panels we will eventually see 3D with out glasses.
theG Posted Oct 10, 2010 7:38 AM PST
Bob, "Glasses-less 3D will never happen" check out [sales link deleted] and what about the 3D Nintendo DS?

Anyway, i dont mind the RealD glasses which will go with my realD projector next year... i hate sgutter glasses tho, expensive and you can see the flickering..
Esther Posted Jul 20, 2011 9:26 AM PST
what exactly do the 3D glasses given out at the movie theaters do? does anyone see a future of 3D movies without the glasses? is it likely that the glasses-less 3D showing technology will ever become commercialized enough to be used as widely as regular 2D tvs that most ppl have in their homes?
Carlos Zacharias Posted Sep 2, 2011 6:00 PM PST
What is the diference: 3 D READY AND 3D? Ex.: Optoma D33 and D66. Whych one is abble to project 3D movies riht now?

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