The word "Ultimate" can mean different things to different people - but the principle is easy to understand.
As enthusiasts, we have been accustomed to routinely having home theaters that better the experience found in regular movie theaters, at least for 2D presentations. Now that 3D is becoming more common, is it possible to build a 3D system for the home that betters what you can find in the commercial theaters? The answer is a resounding YES!
After considering my goals, I tested various methods of achieving this, and benchmarked variables such as lenses and screens, to come up with EASY and less expensive ways to MATCH what is commercially available, as well as more pricey systems to BLOW AWAY what is available in commercial theaters.
At Cedia this year, we saw various 3D solutions which ranged from nigh-on prefect, at $70,000 to $125,000, to various slightly compromised solutions from $4,000 to $15,000.
The new LG CF3D projector was a very nice concept, at $15,000. It packed, essentially, two projectors into one unit, each projecting the left and right light simultaneously, using circular polarisation. However, it suffered, in my view at CEDIA 2010, by not having very good Contrast Ratios in either 3D or 2D modes - something that is not acceptable to me. Also, even with the very best silver screen, ghosting can still be detected at times, due to the nature of circular polarisation, which is a beast to maintain adequately. You can beat this LG system in quality VERY easily by using two cheap DLP projectors, a pair of Optoma 3DXL boxes, and linear filters.
Other systems by JVC, Sony and others, used active shutter systems - flickering the left and right vews, and having active glasses to view them. When I saw these new systems at CEDIA, I was immediately struck by how dark they were in 3D mode, and how some of them suffered from obvious image flickering, which I found too distracting to the enjoyment of the films in 3D mode.
Moreover, all the systems I saw suffered from the typical 24p stutter in fast motion, when showing Bluray 3D. This is typical of all film-based 24 frame per second content. In 2D films it can be tolerable, but in 3D, your mind rips it to pieces as just being wrong and unreal. This is one reason why the ultimate 3D system must include frame interpolation.
When I ran into the Optoma stand at the show, and saw their new 3DXL box, I knew IMMEDIATELY that I could better all of what I had seen, even perhaps match some of the $70,000 systems I had seen at the show. The Optoma 3DXL lets you take a 3D video input, from various formats such as Bluray 3D and DirecTV, and send it to a DLP-Link 3D projector. HOWEVER, when you use two 3DXL boxes, they split these 3D formats into two streams for the left and right eye, and send them to a dual-projector setup, such as the one I visualized.
I had to do it...
A quick primer on 3D systems:
The 3D you see in theaters is typically "passive 3D", that is, you wear a pair of cheap passive glasses, and the light on the screen is polarised, so that the glasses filter the appropriate "side" of the image for your left and right eye. In the theaters, there are basically two ways this is done; the first is using two projectors that are always on, with a separate filter on each projector, and the second is by using one projector and placing an electronic polariser over the lense, which switches back and forth rapidly between the two polarised states, while the projector "flashes" the alternate eye views. This happens so fast, that you are not supposed to see the flickering.
"Active" 3D systems, which you more typically see in the home, uses electronic glasses that open and close each eye while the TV or projector switches images.
Problems with existing systems, particularly in context of home theater:
There are various problems associated with the systems used both in commercial theaters, and in home 3D systems. First, active shutter systems are prone to "crosstalk" or "ghosting" - even the best systems will still show this problem. When I first viewed Avatar 3D on my Panasonic plasma 3D TV, I was surprised to see crosstalk quite regularly in dark scenes with bright objects. And the Panasonic system is arguably the best active 3D system for TV sets - LCD have bigger crosstalk issues than the Panasonic system. Another issue with active shutter is flickering - something that some folks are certainly more sensitive to than others. Another issue is the comfort of the relatively heavy active shutter glasses, and also the cost - usually over $100 per unit. Finally, by flickering between eyes, particularly in a projector application, active shutter systems can routinely "kill" 60% to 70% of the available light, making the images dark and difficult to enjoy.
So I prefer a passive 3D system, but what are the pitfalls of passive systems? In applications where there is a single projector with a switching electronic polariser, one can experience similar issues with light and flickering, athough, commercial systems tend to oscillate at 140 hz, to fast to perceive the switching. Also, within the passive "space", there are three major technologies used: "Linear" Polarisation (typical of IMAX), "Circular" Polarisation (typical of RealD) and a third system, the Infitec color filter system (used by Dolby 3D). Linear polarisation has the best extinction ratio of the two polarised systems, and hence the best image quality, but is subject to reduced extinction ratios when the viewer tilts their head too much. However, I found that Circular had such poor extinction ratios that Linear was still only equivalent to Circular with someone tilted their head, not really worse. Also, Linear polarisation is MUCH easier for a screen to retain than Circular, allowing a greater selection of screens to choose from, and allowing a more flexible system which can be used more easily and satisfactorily with regular 2D content as well.
Although Circular polarised systems will suffer more ghosting than linear, RealD makes it work beautifully in commercial theaters by preprocessing the video to estimate where they will have extinction issues, and applying "corrections" to the video to offset these, resulting to the viewer not perceiving it. Very smart stuff, but not suitable or available for a home theater at this time. However, pretty much all movie theater passive systems I have seen are still based on 24p film, and even when they are double or quadruple-flashed, the motion breakup in fast movement is VERY apparent to your brain. Again, this is something we can better in our "ultimate" system.
With polarised systems in general, the light loss situation can be "bad" or "good", depending on the light output from the projector you choose to use. DLP projectors can be less expensive, and can be very bright, but their light is usually non-polarised. This means that when they are shot through polarised lenses, and then your passive glasses, you will typically lose a little more than half the light output. Projectors such as DiLA or SXRD are typically pre-polarised. This actually works out very well with polarised lenses, as you can end up retaining over 80% of the light output, if you match a particular system with the appropriate choice of filter system. Be aware that you MUST test the light output of any projector you are considering for a passive system, as some LCD and DiLA projectors have some of the colors polarised at an opposing angle to the other colors (ie some Sony projectors) and CANNOT be used in a polarised system at all.
The Infitec system is not currently suitable for attempting to implement in a home theater - at this time. It will lose over 90% of the light output of the projector, and requires special commercial color processing systems to pre-alter the video fed to each projector, to compensate for the very significant color distortions caused by the lenses.
THIS THREAD, is for anyone interested in the subject, to add their thoughts, experiences, and also source materials they have found.
At this point in time - the system I am visualizing will result in a 3D home theater with the following attributes:
(1) A discrete two projector "passive" 3D system, which allows the use of cheap, "passive" theater-style glasses, rather than expensive "active" shutter glasses.
(2) Light output of 96 hz or 120 hz per eye (depending on content) rather than 24 hz, 48 hz or 60 hz of most existing solutions
(3) Frame Interpolated output for each eye, resulting in a higher TRUE frame rate for each eye than source 3D material commonly available. One of the bigest bugbears I have with 3D films now is that a low frame rate is more disruptive to immersion in 3D than in 2D.
(4) A system that will handle all available 3D formats, not be restricted to a particular set of standards of the particular projector used.
(5) A system that will allow you to use regular non-3D projectors, even of disimilar resolutions, to make the 3D theater.
(6) System that allows use of picture enhancement technology that is not currently available for 3D use. For instance, I plan on intergrating two DarbeeVision boxes to enhance the 3D impact.
As they said in Inception "You mustn't be afraid to dream a little bigger".
This thread will allow us to share findings of practical implementations that all sound good in theory, but are risky to invest money in without proof of concepts. Also, it will help show which systems can work, or not work, in a set up.
Ultimately - (1) I will build at least TWO different systems here, one based on linear polarisation, one based on circular polarisation. (2) I will have tests linked showing comparative performance of various glasses and screens used with each solution,. (3) I will be able to recommend a combination for each that gives the best tested results - hence making it easy for anyone to confidently set forth and create their own system.
(NOTE - February 7th, 2011 - after doing side by side testing of circular and linear implementations with my dual-projector RS40s I have come to the informed conclusion that circular is not the way to go for a home implementation, whether home-built, or a commercially available system. Circular polarisation is just to delicate and difficult to maintain in the context of a screen which must also double as a 2D screen. If a commercial solution comes along down the road that does real-time image analysis, to compensate for the ghosting that is inherent to circular polarisation, this may change, but we are not there yet, I fear).
- So, in light of the above, I will now focus on building two Linear systems, one being the "Ultimate 3D projection system" using two JVC RS40 projectors with Frame Interpolation enabled, and superior contrast ratios, and the other being two less expensive DLP projectors, without the benefit of Frame Interpolation. Both systems will perform admirably, and will outperform anything available under $15 K, but may also exceed what you are seeing in many theaters. In particular, the RS40-based system will blow away almost anything else you've ever seen in almost every respect.
I'll discuss how you can build your own system - it's very doable - and this thread will show you how easy it is, as well as guide you in finding the parts and putting them together correctly. I have deliberately tested the "right" ways, as well as the "wrong" ways, so that I can speak intelligently and confidently about my choices, and what they mean to you.
For instance, for some polarising lense kits, the internal polarisation of a particular projector might have a negative impact on final light output. So one of the things I propose that we post here, are our own objective tests on the equipment that we already own, so that this can be shared with others and help in their decision-making.
Another thing that can be posted is WHERE to source some of the parts that can be helpful to creating a system of our own, as a resource to others with the same interest.
Another, might be other processing, or add-on equipment that might be useful in improving the final solution.
Finally, of course, there will be the personal experiences of those who have ventured forth and built one system or another - what worked for them, what didn't, what was the overall result.
I've reserved a few posts below this, which I intend to use as repositories or summaries of some of the knowledge and equipment which may appear in the thread later on...
If you are planning to build a dual projector 3D system, you do not necessarily NEED to become an expert in all these optical "thingies", as I will try to give you easy to replicate systems that I will build and test here.
However, if you still want to try to understand what is happening to make these systems work, I will be linking any relevant documents I run into, here, for your perusal.http://www.drt3d.com/W05-Polarization.pdfhttp://www.meadowlark.com/applicatio...%20devices.pdf