This is topic Definition of "dual digital"? in forum Digital Cinema Forum at Film-Tech Forum ARCHIVE.


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Posted by Mike Croaro (Member # 3123) on 05-31-2009, 12:02 AM:
 
Re: Up in 3D

What is the difference between "dual digital" and regular digital.

See the attached link to the Grand Lake Theatre is Oakland, CA which boasts on their webiste that they are the only theatre in Northern California with "dual digital".

http://renaissancerialto.com/

Mike
 

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Posted by Sam D. Chavez (Member # 1841) on 05-31-2009, 12:48 AM:
 
This was discussed in the thread below, cheap 3D.

I did this project and we used two Christie ZX projectors with passive Master Image Polarizing filters in front of each lens.

One projector is left eye, the other is right eye.

The glasses are the same as other Master Image systems.

There are a number of advantages, there is plenty of light and if 3D goes away, you have a second projector to use for D-Cinema in future.
 

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Posted by Julio Roberto (Member # 4976) on 05-31-2009, 01:10 AM:
 
They mean they are using two projectors instead of one. Imax, i.e., does it this way (with dual-projectors).

This could hold the following (practical) advantages over SOME single projector systems, specially when playing 3D titles:

-Potentially brighter picture, by using two projection lamps instead of one. This could also allow for a potentially larger screen as well, i.e.

-No "3D flicker" (no temporal disparities). This is a slight defect that occurs on single projectors when one eye is seeing one thing that is different in time from what the other eye "remembers". In short: it gives some people some eye fatigue/headaches/weird feelings sometimes. Dual projectors or Sony 3D single projector do NOT need to have this effect.

-Potentially higher quality picture, with double the color resolution (4:4:4 instead of 4:2:2) and larger color gamut (12 bits against 10 bits). Sony 3D single projection system also has this advantage.

-Potentially, a dual projection system could be made to have less ghosting (3D double-images) than some single projection systems. But some single projection systems, like Dolby, can be as good or even better in this department.

-For 2D applications, the screendoor "artifact" could be less visible. Sitting close to the screen, it may be apparent the black space between the pixels, called the "screendoor", on many projectors. By using two projectors together, their screen-door effect could be less apparent by "blurring" together.

But dual-projection can have its dissadvantages. I.e. if both projectors are not calibrated/adjusted perfectly, the images in 3D may appear assymetrical. They need to match in color, brightness (i.e. lamp aligment and output), etc. It's not possible to align the images 100.00% identically, so there is always some (very) minor keystone disparities between the images, etc.

Also, specially if placed side-by-side instead of one on top of the other, they could show assymetries in silver screens 'cos of the hotspots being (slightly) different for each image.

And, of course, it can cost twice as much as a single projection to buy and run (i.e. two lamps/double the electricity).
 

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Posted by Frank Angel (Member # 248) on 05-31-2009, 02:11 AM:
 
When using dual projectors, wouldn't any standard passive polarizaton filters work just fine? Why would you need to use Master Image polarizing filters and glasses, i.e., couldn't you use any circular polarization filters and glasses (or even the older horizontal/vertical polarization)?

PS -- can someone explain the meaning of 4:4:4 and 4:2:2 -- thanks.
 

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Posted by Julio Roberto (Member # 4976) on 05-31-2009, 09:52 AM:
 
Master Image also offers passive polarization filters:

http://masterimage.co.kr/new_eng/product/system_02.htm?pos=22

You could, indeed, use linear polarization instead of circular like it has been the preferred method in the past (i.e., Imax Prime ). It would have a slight advantage in brightness, ghosting and cost over circular. With the drawback that is more sensitive to geometrical angle-dependant performance (i.e. patrons need to keep their heads perfectly leveled or ghosting starts to appear, worse for larger screens or steep projection angles, etc).

4:4:4 and 4:2:2 are terms used in the video industry to refer, in short, to how the video signal is sampled. The video signal usually travels in 3 components, like 3 signals, which could represent each primary color (i.e. Red Green Blue) or a multi component signal (i.e. luminance+2 channels of chrominance).

What it means, in short, is having X number of pixels in one channel, typically the luminance channel (Y or the "black and white image") and a relative number of pixels on the other two channels (i.e. the "color difference channels"). So for 4:2:2 it could mean, i.e., that for each 4 pixels on each scanning line in the first channel, there are 2 pixels in each one of the other 2 channels horizontally and another 2 in the next scanning line.

There are many variations of this and sometimes the notation is not all that ... there. But it's a way to talk about "stuff" in the image, like color, having more or less resolution than other "stuff" in the same image, like some other color channel or luminance, and how the (sub) samples are located in the image vertically and horizontally compared to the main (not sub-sampled) channel.

Here it's better explained:

http://en.wikipedia.org/wiki/Chroma_subsampling
 

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Posted by Monte L Fullmer (Member # 2797) on 05-31-2009, 08:45 PM:
 
Looks like SONY is on the 4:4:4: program well enough with their 4k units.

This might be the way to go for both 2d and 3d projection ...

For I'm one of them that can call tell that 4:2:2: 3d isn't really for me for I do experience slight effects (like mild eye strain for beginners) of the triple flash, alternating eye presentations...
 

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Posted by Mark Gulbrandsen (Member # 72) on 05-31-2009, 09:52 PM:
 
Monte,

Dual projector 3-D is stuck at 4:2:2 for now because only one HDSI output on the server feeds each projector... limiting each proj. to 10 data bits. That of course could change and is a clear advantage to having two projector 3-D instead of just one.

Mark
 

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Posted by Julio Roberto (Member # 4976) on 05-31-2009, 09:58 PM:
 
Mark forgot to mention that the Qube server comes standard with dual-dual SDI connection (and thus, capable of 4:4:4 12bits 3D for dual-projectors) and that it's an option on other servers as well, such as GDC's, for example.

The Qube is capable of decoding two separates full quality 2K packages simultaneously and comes standard with quad-sdi, so I see no reason why they wouldn't decode a 3D 48fps at full quality feeding each dual-sdi output, unless Qube engineers were really lazy that day ...
 

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Posted by Mark Gulbrandsen (Member # 72) on 06-01-2009, 08:54 AM:
 
I didn't mention it because I'm not sure the dual outputs will fuinction in 3-D mode or not. They very definately will in 2-D.

Mark
 

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Posted by Jack Theakston (Member # 4484) on 06-02-2009, 01:40 PM:
 

quote:

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-No "3D flicker" (no temporal disparities). This is a slight defect that occurs on single projectors when one eye is seeing one thing that is different in time from what the other eye "remembers". In short: it gives some people some eye fatigue/headaches/weird feelings sometimes. Dual projectors or Sony 3D single projector do NOT need to have this effect.

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quote: Frank Angel

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When using dual projectors, wouldn't any standard passive polarizaton filters work just fine?

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quote: Manny Knowles

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Is dual-projector a "3D-Only" format, or are these setups ever installed/used for 2D?

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quote: Manny Knowles

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Next question: Do all dual systems use a beam splitter?

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