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This topic comprises 3 pages: 1 2 3
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Author
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Topic: RealD,Dolby3D,Xpand vs dual-projector setup
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Nastia Motovilova
Film Handler
Posts: 30
From: Nicosia, Nicosia, Cyprus
Registered: Sep 2012
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posted 01-05-2013 04:15 AM
Hello to everyone,
As I am new to 3D tech and I'm trying to clear a few thoughts and was wondering if you could offer some insight.
My question is, if there was a choice, would you go with a "traditional" 3D dual projector setup whereby one projector is for the left eye and the other for the right with the static filters in front of the projectors (of course properly aligned) or would you go with one out of the three, Xpand,Dolby, RealD?
This is for a DCI projection system, for an only 3D cinema, using a silver screen (though the silver screen can be replaced if need be). With the dual projector linear polarized set up, there would be some loss of brightness when the image passes through the filter in front of the projector and again when it passes through the glasses. However, with a dual projector set up, there is a benefit of the increased brightness.
There are other benefits as well, such as not needing to go with a trademarked system which bears license costs of buying the 3D technology, relying on a third party for repairs, potential license costs etc
I would really appreciate your opinion on the above.
Regards
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Antti Nayha
Master Film Handler
Posts: 268
From: Helsinki, Finland
Registered: Oct 2008
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posted 01-05-2013 05:17 AM
There was some discussion about the options earlier in this thread.
First up, dual-projector 3D is a good idea, particularly now as the industry is trying to raise the standards for 3D light levels.
Second, any silver-screen based 3D system will compromise your image quality – even more for the 2D content. That leaves you with XpanD and Dolby.
I have no personal experience with dual-projector XpanD, but it’s only common sense that you have to be extremely careful with the alignment of the two projectors as any inaccuracy comes off the resolution.
On the other hand, dual-projector Dolby 3D is a ”traditional dual setup” in the sense you described: each projector is only projecting one eye through a static filter. You should still try to align the two pictures as precisely as possible, but it’s still less critical than XpanD since the eyes are able to correct for slight inaccuracies between them. Dual-projector Dolby 3D is also a bit more light-efficient compared to single-projector Dolby, because there’s no dark time involved. And of course, Dolby’s passive glasses are much less hassle compared to XpanD.
Christie is selling a dual-projector integration kit called Christie Duo, which might be of interest for you. All the four major 3D systems are supported. Of course, a similar system can be built with Barcos – it’s just that Christie has made an ”off-the-shelf” product out of it, complete with a stacking system and a camera and software for automatic alignment. (I wouldn’t bother with NEC projectors for such a setup, due to light efficiency and lamp life issues.)
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Marcel Birgelen
Film God
Posts: 3357
From: Maastricht, Limburg, Netherlands
Registered: Feb 2012
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posted 01-05-2013 05:28 AM
First of all, Xpand, Dolby3D and RealD all support dual projector setups for increased brightness in large venues.
Xpand has both an active and a new passive polarized system and there are others to consider, like Masterimage.
Of all the 3D technologies mentioned above, only RealD has a recurring licensing fee, the others are one-off.
None of the newer systems use linear polarization (only IMAX 3D still uses linear polarization, but that's not an upgrade, but a complete system). That way, you can tilt your head slightly without blurring the image too much.
Xpand has an active system, using shutter glasses and Dolby3D uses a system with alternating primary colors. Both Dolby3D and Xpand work with white and silver screens.
Xpand (the active system) and Dolby 3D use recyclable glasses. The others use glasses that are, outside of the USA, usually bought by the customer for a small fee. Those glasses can then be used at a next screening, if they don't forget to bring them along.
The Xpand (active) and Dolby3D systems are the best systems regarding ghosting. All other passive systems suffer some ghosting. Ghosting is especially annoying if you're using subtitles frequently.
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Marcel Birgelen
Film God
Posts: 3357
From: Maastricht, Limburg, Netherlands
Registered: Feb 2012
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posted 01-05-2013 07:30 AM
quote:
I understand the weight complaints, but surely the active system should be brighter? [Confused]
I don't have the actual numbers at hand, but an active system isn't necessarily brighter, you still loose a lot of light with the glasses. Look trough a shutter glass that's open and you'll see for yourself, the loss is often larger than that of a normal polarizer glass.
Additionally, you go from white to silver screen, which is much more reflective. In this particular case, the image was brighter with the passive system than with the active system, but part of it might also be due to the leakage between left and right resulting in said ghosting.
quote: Antti Nayha
The same with Dolby 3D, except that it’s based on split-spectrum technology so it doesn’t require a silver screen.
Please note that the Dolby 3D filters are installed inside the projector, in the light path in front of the imager. That's true for both the "split" and "uniform" filter.
It's also possible to run Dolby3D in a dual projector setup with spinning filter, a lot like Xpand (active) in dual-projector setup would function. In that case, you indeed need to align your projectors perfectly.
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Antti Nayha
Master Film Handler
Posts: 268
From: Helsinki, Finland
Registered: Oct 2008
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posted 01-05-2013 08:06 AM
quote: Marcel Birgelen
Look trough a shutter glass that's open and you'll see for yourself, the loss is often larger than that of a normal polarizer glass.
These things can be hard to judge with a naked eye. It’s a common misconception, resulting from an optical illusion of sorts:
Remember that in an active system, there are no filters in the projector. This is why the image is very bright on screen, and most of the light loss takes place in the glasses. The difference between glasses on vs. glasses off appears huge, and you will go around telling your friends that the active system is darker because ”you can see it with your own eyes”.
In contrast, most of the light loss in passive systems happens already in the projector, and the glasses themselves don’t cut that much light. (I’ve even heard educated people claim that putting on the Dolby glasses actually makes the image brighter! ![[Cool]](cool.gif) ) But if you look at the net efficiency of the complete system, an active system usually wins: all other things being equal, you get more foot-lamberts in the eye per a watt of xenon light. Which is what matters, of course.
According to the usually quoted figures, the XpanD active system should be around 50% brighter compared to Dolby. That is probably overstating it a bit, but RealD XL is still the only passive system that actually gives you more light than active systems. And RealD XL has its own issues.
That said, and back on topic: even though Dolby 3D won’t win any light efficiency awards, it remains a good choice for both single and dual projector installations.
quote: Marcel Birgelen
It's also possible to run Dolby3D in a dual projector setup with spinning filter, a lot like Xpand (active) in dual-projector setup would function. In that case, you indeed need to align your projectors perfectly.
Yeah, I’ve heard about this… but it puzzles me as to why would you ever do it? In addition to the alignment issues, you will need to set up a dark time which naturally eats up light. Plus you end up with expensive moving parts in the projector. The only advantage I can see is that you can still run 3D if one projector breaks down – but it’s not going to be very bright 3D.
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Marcel Birgelen
Film God
Posts: 3357
From: Maastricht, Limburg, Netherlands
Registered: Feb 2012
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posted 01-05-2013 09:56 AM
quote: Antti Nayha
According to the usually quoted figures, the XpanD active system should be around 50% brighter compared to Dolby. That is probably overstating it a bit, but RealD XL is still the only passive system that actually gives you more light than active systems. And RealD XL has its own issues.
I agree that those things are hard to judge with eyesight only, although it's the end result that counts.
They came from Xpand 3D active and went for Xpand 3D passive. Maybe the polarizer Xpand uses is more efficient than the Z-Screen RealD uses. It still looks like a "Z-screen" type polarizer, not like the RealD XL polarizer. I don't know why you would otherwise switch from a perfectly OK active system to a passive system. They only switched it for their larger auditoriums, the smaller ones are still on Xpand Active.
quote: Antti Nayha
Yeah, I’ve heard about this… but it puzzles me as to why would you ever do it? In addition to the alignment issues, you will need to set up a dark time which naturally eats up light. Plus you end up with expensive moving parts in the projector. The only advantage I can see is that you can still run 3D if one projector breaks down – but it’s not going to be very bright 3D.
I also don't know why you would try to do this. It would only make sense in an odd projector setup, like with three projectors.
Afaik, the "color wheel" is still rotating inside the projector, even in a dual projector setup with a split left-right, but that's primarily due to cooling.
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Marcel Birgelen
Film God
Posts: 3357
From: Maastricht, Limburg, Netherlands
Registered: Feb 2012
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posted 01-05-2013 10:48 AM
I guess you want to be able to run encrypted DCPs and want to be fully DCI compliant or not?
No matter if you choose RealD, Dolby 3D, Xpand or almost any other competing 3D solution, it will practically always be cheaper in a single projector setup than with a second projector and a "roll your own 3D" setup. A DCI compliant projector starts anywhere around EUR 35K and goes all the way up to infinity. Almost any single projector 3D setup can be had for less than that.
If you're going to do 3D your own way, you need to be aware of the possible complications:
1) Where do you get your glasses?
2) Support from your playback solution, like your Playback server and IMB/Server combination.
3) Positioning your polarizers correctly.
4) Getting your polarizers out of the way for a normal 2D presentation.
So, unless you either have a really big screen and need two projectors and you do not have the few extra bucks for an "industry standard" 3D system, I would just go for a standard, off-the-shelf system.
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Marcel Birgelen
Film God
Posts: 3357
From: Maastricht, Limburg, Netherlands
Registered: Feb 2012
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posted 01-05-2013 11:28 AM
quote: Nastia Motovilova
Yes, the system needs to be DCI compliant. Is it a requirement that a DCI compliant system implements one of the available technologies as these technologies have been officially approved?
Or can one create his own 3D DCI compliant system by using linear filters, as long as the projectors and the server are both DCI approved?
In theory you could. Only don't underestimate the potential issues with getting the polarizers right and controlling the polarizers, if you don't want to move them manually each time you're switching from 2D to 3D.
If you choose a 3D system that's fully supported with your Playback server, then you also can control this system via your system. Most systems out there have dual-projector support.
A major problem could be the ghost busting functionality, because your server might not be capable of enabling that on an unknown system.
quote: Antti Nayha
I know of some theatres that have done just that, even though the passive system of their choice gave them less light. A major factor can be the fact that active glasses require active maintenance, with all the associated costs.
I will certainly ask them. Because now both their 2D and 3D are screwed. The 2D now suffers from hotspotting (just like the 3D of course) and unnatural looking colors and the 3D is just worthless with that amount of ghosting. Maybe that can be fixed with a better adjustment of the polarizer or maybe the ghost busting feature was not working, but still, it's a step backward if you ask me.
quote:
XpanD’s machine-washable X101 glasses are also heavy enough to irritate a lot of customers. The lighter models are more convenient, but then you must either have the staff clean them up manually (even more hassle) or hand them out unwashed along with disposable cleaning wipes, so the customers can do the dirty work themselves (also irritates them)…
You're right, those things start to suck after an hour or so of wearing them. I would really want them to innovate on that, getting lighter active glasses that are dish-washer proof...
quote: Antti Nayha
There’s a lot to like in active 3D systems, but I wouldn’t recommend them for every theatre.
That's why I like Dolby 3D the most, if it's done right. You need a lot of light, but your glasses are acceptable in terms of weight and you have almost no ghosting.
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(At least if that was a single-projector setup.)
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