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Author
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Topic: Digital 3D Systems (DLP), Pros and Cons
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Steve Guttag
We forgot the crackers Gromit!!!
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Posts: 12814
From: Annapolis, MD
Registered: Dec 1999
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posted 06-19-2010 12:59 PM
Okay...somewhere, there is a DCinema pro/con thread and Tech 3D really belongs in the Film forum (it is film)...so lets talk about the DIGITAL 3Ds out there for the DLP systems. I've installed three, and not surprisingly, have formed an opinion of them! (and have a forth system in one of my screening rooms)
Let this be a discussion of the TECHNICAL merits/problems of the systems, not the financial side as those are covered in other threads or should have their own thread.
Dolby 3D
The first for me is also my favorite: Dolby 3D
Not not because it is Dolby (or Infitec) but because it allows 3D on a non-silver screen. It is a system that allows excellent 3D reproduction anywhere in the auditorium. And, to my eyes, the images look better than those on a silver screen.
Dolby is the only system that color corrects for each eye too. Now the polarized 3D system should not have color issues since they should be neutral in density but still, the Dolby calibration has one color balance each eye as well as set the light level for each eye.
The chief downside of the Dolby 3D system is the light...or lack there of! When things are going your way, you get a 10% through put with the system. That is, if you have 50fL on your screen in 2D...you will likely only have 5fL by the time you color correct/drop the color wheel in/ and measure through the glasses (what one really sees). I have one system that only achieved 6% so even starting with 50fL only would yield 3fL (too low...thankfully I have headroom built into my systems). This may make one want to install a gain screen of 1.4 - 1.8 but try to resist that...as you go up in gain, you will loose the even illumination and optimal viewing from all seats. Remember too...if you put in a gain screen, you only get that gain at ONE POINT of the screen...you will likely have lower illumination from over half the screen...unless you curve it.
I STRONGLY recommend that with Dolby 3D, IF YOU HAVE SIDE MASKING movable, use an Anamorphic lens. Yes it costs a boat load of money but that is a one-time purchase. It will yield you 20-25% more light (depending on the system and which lens you use). Anyone with a typical cinema with side movable masking that isn't using an Anamorphic is "doing it wrong." The light needed for that Scope image versus the Flat image is far too big a spread
A big plus to Dolby too is its "automatic." That is, you can have your server/player turn it on/off as part of your show without operator intervention. It is the only 3D system that does that, out of the box.
Dolby's disc sits just before the integrating rod and is part of the "clean" light path so minimal to no maintenance is required.
Some manufacturers also offer the Dolby 3D system pre-installed.
Dolby has a manual for there system though the actual color wheel installation isn't very well documented, except for the Barco integrated wheels (Barco documentation). That said, the concept of where the color wheel goes and how it mounts shouldn't mystify one too much, if are competent at such things.
Master Image
Master Image uses a spinning disc infront of the projection lens. And boy does it spin... 4320 RPM
On the up side, its 3D quality is the best I've seen on a Silver screen (and yes, it requires a silver screen). No ghosting and the through put is about 18% on the light. So, to hit 5fL in 3D, you need about 28fL on 2D.
There are a couple of down sides to it. It is a dirt magnet and requires cleaning on a regular basis (your booth conditions will dictate the frequency).
It is NOISY. Nosier than most any film projector I've heard. You best have double-glazed port frames and good sound isolation on your walls or you WILL hear it in the theatre.
The factory doesn't seem to provide any means (or none that have been documented to me) for controlling it externally...though I'm sure one can "rig" it). Thus this thing will be spinning, in a typical booth, all day. It "idles" at 2880 RPM...slower but still a pretty good clip.
In the event that 3D dies out (we can only hope)...Master Image should have no trouble getting into the Anvil business! This thing is HEAVY...which is good due to its location (in front of the projector) and the vibration/speed it runs.
Since one doesn't spend a lot of time calibrating this system and interfacing it...it is a VERY fast installation. Set the raise/lower limits, position it in front of the lens, connect the supplied cable...done. It just works.
Documentation is more than wanting...especially for the price that is charged for the system.
Real D
Real D should really be broken into two sub categories...Z-screen and XL.
If at all possible, always get the z-screen and not the XL (more on that later).
Real D is a silver screen system (boo!) like Master Image. However it is the weakest, in terms of 3D. It requires some form of ghost busting or you will see shadow images of the wrong eye. The studios will no longer distribute ghost busted images so now, the servers/players must do it real time. My experience has shown that it doesn't work phenomenally well. That said, I have not seen the real time ghost busting on enough systems to know if it was the particular servers or just the process is flawed and is being passed off as "good enough"
Installation is pretty much a breeze on most projectors though the support can be a bit flimsy, depending on the projector model. The mount may restrict opening the projector for service or require removal of the brackets to open the projector.
The system does not automatically insert/remove itself but it can be done quickly...still I prefer that these systems be able to automatically, by virtue of the show build up, move into place or remove themselves. There are some manufacturers that are using their anamorphic attachment mechanisms to "swing/move" them into place.
Light throughput is about 15% (50% more than Dolby but 17% less than Master Image. One should remember though...these are silver screen systems where the gain is typically 2.2-2.4 and the light is typically read at the center of the screen so there is a 2X boost to the light there.
Real D XL
The XL version came out to bring more light for big theatres and that is the ONLY time it should be used! It does get one more light. It has a 28% throughput. Making it the most efficient single-projector 3D system.
This contraption mounts in front of the projector and is HEAVY (something like 40lbs). It has a single inlet but a dual outlet (over/under). There will be two images coming out of it so you will need a TALL port. If you are curious if your port is big enough...measure the height of your existing image, and then add TWO more images of the same size on TOP of that...if you can get that top most image out of your existing port, you'll need to get a bigger/taller port.
Installation can be slow going, depending on your booth/theatre layout. One has to match the upper image to the lower image so that just a single image is presented on screen (they are from the same eye. After all, the second image is the reclaimed light. You have to match in vertical horizontal and in magnification. The more orthograph your system is, the easier it will be to accomplish. If you have a curved screen...you've lost the battle already. Getting two starting points to curve a line identically just isn't going to happen (at least not with this system). Remember, these to images are not Left Eye/Right Eye...they are the SAME eye!
The better you get the two images to converge, the higher the resolution the picture will be. Thats right, you can expect the image to have less resolution when you are done...if you get it perfect (and you can get it pretty darn close, everywhere) then you are, theoretically, back to the full resolution. I suspect that most people match the center up pretty well but have a hard time in the corners getting them to match too.
One thing I'm impressed with is the alignment gauge. It is slicker-n-snot. Don't be foolish and use a bright target to align with (the gauge is white)...use a nice simple cross hair pattern...the "tennis court" pattern will do if yours has the center cross hair. You can get that crosshair to easily show up on the gauge and have you set height/tilt perfectly.
The brackets for the XL are cumbersome at best on a Barco installation. They mount to the pedestal and block you from removing the front cover of the projector for service.
You will more than likely need separate "screen" and "lens" files for the 3D formats if you have an XL as it does alter magnification some.
So, my STRONG recommendation is...if you don't "need" the extra light that the XL offers (you are at the max of your projector's lamp and still can't hit 5fL) pass on the XL and insist on the Z-screen, if you are going the Real D route.
There are documents for both the Z-screen and XL...not great documents but enough to get you through...they don't ship with the unit...you need to download from the Real D site (passworded FTP site). Real D also has targets on that site for the pre-full-frame triple flash (1920 based) projectors (EFIB boards).
ExpanD
I have not installed this system but have one client that has it. The 3D effect is excellent and installation couldn't be easier...just a transmitter for the battery powered glasses to receive. It, like Dolby, works on any screen, including white.
All systems
One should optimize as well as possible the settings in the "3D" file of the projector you are using. Normally there is a starting point that is documented/provided. Use a good 3D target (like Dolby's Sync Delay) to ensure you are seeing the correct eye and that you are centered on your delay/dark time.
Double/triple check your "Eye Dominance" setting (and it changed between series 1 and series 2 projectors). On series 2, I've found that "LEFT" is correct for Dolby and Real D...whereas "Right" is correct for Master Image. Having this set wrong will cause an odd jittery effect only to the moving objects while the stationary objects look fine. Try it in both settings and you will see the effect...in the wrong setting...aside from the twitching, you will feel MUCH more eye strain.
-Steve
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