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John Sciacca Writes...

Features, Reviews and a Blog by John Sciacca

Random Thoughts (Blog)

Random Thoughts (Blog)

Should You Really Avoid Stacking Projectors for Passive 3D?

Posted on March 10, 2011 at 3:02 PM

There was a blog post a few weeks ago titled “Four Reasons to Avoid Stacking Projectors for Passive 3D Installs.” I read it. Chances are you read it too. (Come on, you know you can't get enough about 3D!) And after reading the post I thought, “Yeah, those are all good reasons why you wouldn’t want to stack projectors. Heck, I don’t even really want a SINGLE 3D projector, let alone two of them! Now, what shall I do with all that money I just saved?"

But then I remembered that the best 3D projection experience that I have personally witnessed to date was from Runco when they debuted their D-73d projector at CEDIA 2010. From my blog posted at the Expo, I wrote, “Fortunately the 15 minute walk [to the demo] was totally worth it as the Runco demo had the BEST 3D I’ve seen so far at the show. (At this point, I feel like I’m a qualified expert since I believe I have seen all the 3D demos. ALL...OF...THEM!) They have licensed Real-D’s technology and use a passive system that is the closest thing (identical?) to what I’ve experienced in the theater and didn’t make the two hemispheres of my brain feel like they were trying to slowly tear apart, swap places and then wage war on each other.”

Then, I happened to attend the Runco Training Academy at their facility in Beaverton, Oregon. (You can read about my experience here.) And there in the training room was the D-73d in all of its double-stack projector glory! So, since the author of the initial post, George Walter, was VP of home cinema for Digital Projection, Inc. – a company that produces a single-projector 3D solution – I felt it only fair to pose his four “reasons” to Runco and let them address them. Tit for tat as you might say. Well, if you were British and a character out of an Agatha Christie novel you might.

Runco immediately agreed that there are definitely potential issues with double-stacking projectors but Chief Architect, Bob Williams commented, “We see the issues mentioned as engineering challenges to be solved.”

Runco VP of Marketing, Jennifer Davis added, “I find it interesting that people believe passive 3D to be so compelling that they’ll do anything, including complicated scaffolding rigging of two projectors to attempt superior 3D.  There is a reason why people are trying. Runco could have advised for years that people stack our projectors, but we share the concerns that have been raised about this kludged approach.  The problem with simply stacking projectors, as these articles state, is that managing two projectors is complex and can lead to bad experiences.  Issues of convergence, focus, complexity, cost, and lack of flexibility options top that list.”


It goes to reason, when you have two projectors you have two optical paths to the screen and you need to have those optical paths in perfect alignment – or convergence –  to produce a great image. And if anyone has ever performed a CRT calibration – or, dear, sweet baby Jesus, a DOUBLE-STACK CRT calibration! – then you’ll know that it can be tricky to get the best result.  Williams stated, “Double-stacking projectors has been around since the beginning of projection [and] with the correct design, you have almost two identical light paths to the screen.”

Davis adds, “Unlike two projectors that are installed separately, our D-73d chassis is a single projector that is easier to install than two projectors.  Mechanical precision and tuned electronics allow you to converge the images.” Runco feels their “2 in 1” chassis design makes the lenses almost perfectly aligned, and with a lens separation of only 8 inches, there is much less adjustment to be made.

Once the lenses are mechanically adjusted, a lock screw is tightened so “there will be absolutely no drift of images because it is a digital device” according to Williams. Further, Runco’s new Digital Compass allows aligning the secondary image to the primary with a plus/minus one-half pixel tolerance ANYWHERE on the screen.

Here's what the Digital Compass Calibration screen looks like:


The point here was that with two projectors, neither could be in the perfect position and that one would need to be so low that it might shine into the back of chairs of the head of a viewer.

Again, with a properly designed system built around two-projectors from the get-go, the cabinet size and lens separation can be minimized. Davis noted, “Most two projector set-ups use an industrial mount that can add extra inches of space between the lenses, as the height of the chassis, curves of the projector, and the mount must be accommodated. “

Now, I’m not going to say that the D-73d solution is small. In fact, it would look pretty frickin' mighty hanging from a ceiling, especially with the DOUBLE anamorphic lens kit in place. Anyone walking into your house for the first time is likely to be all, "Oh, and this must be your movie room, I see your speakers and scre... Holy CRAP!!! What is that thing hanging from the ceiling?! It's huge!" To which point, if it is a man, he'll probably look at you all starry eyed and want to chest bump you or shake your hand and buy you a beer and ask how in the world you talked your wife into letting you get one. And if it's a woman she'll likely shake her head in mild disbelief, possibly muttering, "Boys and their toys..." under her breath and then go off and try and offer comfort and succor to your significant other. And you would definitely NOT want this bad boy to come crashing down on you; all 100 pounds of 3D might-and-fury landing on your head-brain would make 3D nausea and fatigue look like a week-long trip about the SS Pleasure Cruise. Suffice to say, mount this thing deep into wood or metal blocking. Deeeeeep.

However, with the projector design, the primary lens has a 60% offset, meaning it can be up to 10% above or below the top or bottom of the screen. When you figure the height of most screens and how they are mounted, this will put the bottom of the second lens well above any interference.


This had more to do with the signal being pre-processed and split with left and right eye content going to the appropriate projectors, but I thought I would talk about install complexity here as well, primarily as it relates to the convergence issue above. So, they let me try my hand at converging the system. And I had it totally dialed-in within about 10 minutes. At another point, we changed screen sizes – from a 12-foot wide 2.35x1 screen to an 87-inch wide 16x9 screen – which required a complete cal redo. We had the system totally reworked in about 15 minutes, mechanical lens shift, focus, convergence at all. As far as complexity goes in the install process, it is a non-issue.

As far as “no retail processors [being] available that can break down a HDMI 1.4a 3D signal to discrete left and right eye with HDCP handshakes,” well, the system seemed to work flawlessly at Runco. Sure, it requires an imposing 6U stack of processors, one to split the signal and one for each projector, but it worked. On every Blu-ray, DirecTV, and PS3 game we threw at it.

Commenting on this issue Davis said, “It requires 3rd party processing to split the signals appropriately to each projector which introduces new brands, new incompatibilities, and new points of system failures.  As many have said, there are no retail processors available that can break down an HDMI 1.4a 3D signal into discrete left and right eye with HDCP handshakes.  Well, that isn’t entirely true.  The 3Dimension processor, a Runco exclusive and the result of multiple man-years of development time by our top architects, software, and electronics design teams, delivers the best, most compatible 3D processing available and delivers a unique and distinct picture show to each eye.”

Here's the back of the 3Dimension processor stack:


OK, not to be splitting hairs here, but the primary 3D projector that Mr. Walter’s company sells, the Titan 3D, retails for over $80,000 so, I’m not sure I’d be lobbing stones into the “higher costs” pond. But, anyhow... Yes, two projectors are going to cost twice the price of a single projector. And a V12 engine is gonna run more than a V8 or V10. Meaning that you're gonna pay more for that new Lambo Aventador than a "cheap" Gallardo. But such is life in the world of premium luxury. One of the bigger issues he raised is the two projectors means “more lamps to consider” and beyond just the cost of the lamps, “integrator will also have to monitor lamp life and performance in both projectors to ensure that content for one “eye” does not become brighter than the other.”

And this is actually a HUGE factor to consider. Beyond the lamp costs -- which can be significant on high-end models -- you will need to make sure that the images are maintaining not only consistent brightness but color accuracy and grayscale uniformity between both images over the entire lifespan of the bulb AND from strike-to-strike as the projector lamps turn on. One way to eliminate this cost and worry is by eliminating the lamp completely. Which is what Runco did. Their double-stack solution is a lampless design that uses LEDs that are rated to last the life of the projector with less than a 10% drop in light output over that span. But what about the color tracking issues? Williams said, “A built-in tri-stimulus colorimeter for each light engine takes calibration readings on each and every start up insuring accurate, calibrated color each time.”

Now, I know that this might seem like a Team Runco PR post extolling the virtues of their technology, but that’s really not the case. The truth is, I don’t have a dog in this fight and am not really crazy on the whole 3D craze at all. (Perhaps an understatement if you consider this post...) What I can say is that I’ve spent an entire day – as in a FULL 8 hour day – viewing a variety of material on the D-73d and I can say that it is the most compelling 3D image that I’ve seen and was the easiest on my eyes to view even over an extended period of time. I am definitely prone to 3D viewing fatigue and discomfort, and to my eyes Runco’s solution best addresses this issue. And while these might very well be four compelling reasons to avoid a double-stack, it seems like Runco has offered four compelling solutions to address them.

I’ll also say this, at this point in time, if I were in the market for a $70,000 projector (the price of the Runco stack with the optional anamorphic lens system; you can read more about my love for anamorphic here...) the Runco would definitely be on my short list. Sadly, I'm not. But if anyone wants to chip in, I'll save a pair of glasses and a good spot on the couch for them.

Categories: March 2011, 3D TV

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1 Comment

Reply PastorBrad
1:22 AM on February 11, 2018 
All 4 of these children were taken from their mother who doesn't have custody and fled out of the county with them.
July 4th they left from Lost Angeles airport and their final destination was Paris France.
We do not know the whereabouts they may be now. They could be anywhere in the world.
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