Dangers of Stacking Projectors for Passive 3D

From the title of the article I was expecting read about how some poor guy burned his house down after setting his screen on fire from all the photons two projectors bounced off it.

These aren't really "dangers" - things to be avoided entirely because they cause damage or bodily harm. The article more accurately describes challenges - things that can be overcome with thoughtful solutions, and/or drawbacks - crappy things you might have to put up with.

No kidding, talk about overkill. This guy was clearly trying to talk people out of using two inexpensive projectors and passive 3D. Of course convergence is the real challenge, but it is not mission impossible. In fact, it just takes patience. The one thing he didn't mention was the need of a silver screen. For me, this is the only reason I am not using dual projector 3D. I prefer having the speakers mounted behind the screen. Until you can buy DIY AT screen material capable of passive 3D, I will stick to 2D.

Still, your theater will not explode if you go with dual projectors. Lets pull back the hyperbole.

This article needed to be written by somebody that actaully set this up recently. I don't see the purpose of it even without that experience.

It's far more complex to setup, sure, and the lack of available equipment is certainly a problem. That said, for those of us who can't use Active Shutter glasses due to comfort and/or health reasons (nausea, sickness, etc), this is the only route until Dolby 3D or other passive 3D projection technologies become mainstream. I really think that in the next few years, you'll see projectors go entirely Passive 3D on the reference models, and flat panels will make use of "traditional" Active Shutter glasses for convenience.

Until I can get passive 3D for a reasonable price, I'm stuck in my 2D world. Which is a bummer, because 3D content like Toy Story 3 and Tron: Legacy was awesome in the theaters, and I'd love to bring it home.

"Editor's note: George Walter is VP of home cinema at Digital Projection, which offers single-projector 3D solutions."

I think the introductory note says it all.

What a joke.

Polls conducted on AVS have shown that we don't care about 3D. So why do you keep bringing us articles about it?

I tried this four or five years ago. I even bought a projector stand that could accomodate three projectors, each with their own pan/tilt/rotate. The stand was used in days past for aligning slide projectors (I assume for 3D). It was very well built.

Anyways it was a REAL PAIN IN THE BUTT to set up. I'm not sure I was ever able to line it up perfectly but I was able to try it out using a computer for input and computer LCD Shutter glasses. It wasn't worth the effort and I sold everything.

Fun to try but not worth the investment, even with cheap projectors.

I have seen forum posts with more cohesion and better arguments.

Should have been called "Items to consider" but the last paragraph gives it all away.. its a shill for this guys single lens 3d company.

So we assume the guy has tried this with the 3D-XL and a couple of projectors with good lens shift? I only comment on this because the game has changed on this and early reports are looking very promising.

He should of brought up a lot more about screen materials and polarization issues to really make it usefull. That is where the real trouble starts.

For those who aren't interested in 3D, stop reading NOW.

"Danger" is a strong word. I, too, thought the worst when I saw the subject line, but George sound's like someone who hasn't tried stacking projectors or is trying to talk himself out a of dual projector 3D system.

I have two Panny AE2000 projectors stacked and they work great that way. Fortunately, the Pannys look like they were designed to be stacked; nice square contours and a flat top. Other projectors may not lend themselves to stacking quite as well.

For alignment (rarely needed once done), I just turn on the projectors' own focus target which has a good resolution pattern in the center and crosshair targets in the corners. Using zoom, and horizontal and vertical shifts, an excellent registration (more than adequate for 3D) can be achieved. However, no matter how good the registration, I wouldn't choose to use both projectors simultaneously for 2D. There is always some pixel level mis-registration which will show up as blur in portions of the picture, and both projectors aren't needed for 2D anyway. I alternate projectors for 2D just to equalize bulb life, and runtime. (Never had a problem with brightness differences.)

That said, dual projector 3D is an excellent choice with the exception of cost of the additional projector (although compared to the prices of some "3D projectors", its still a lower cost). No flicker, high brightness, and lightweight, cheap glasses. A good 3D home cinema setup cannot only rival the average theater, but best it. The only "danger" is going broke when you have to replace two projection lamps if they go out at the same time.

I am looking at setting up my own passive system, I understand the idea of the dual projector and silver screen but i need to know about the media you can use and what signal goes to what projector? what type of circular filters can be used? Can anyone give me some pointers

Flix,
Check out this thread.
http://www.avsforum.com/avs-vb/showthread.php?t=1280393

It covers a lot, but it will answer your media questions too. But basically, you're looking for a 3D Demultiplexer so that you can use other 3D media solutions with your 2PJ 3D system. The $800 pair of 3DXLs are so far the only game in town, but there are some other solutions in the wings.