Film-Tech Forum ARCHIVE: Preliminary question on video projector "stacking"

This is topic Preliminary question on video projector "stacking" in forum Film-Yak at Film-Tech Forum ARCHIVE.

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Posted by Frank Angel (Member # 248) on 09-10-2007, 09:38 AM:

I was just told that the producers for the park venue that I work during the summer are working with Barco to get an in-kind donation of video projection equipment to "compliment" the 35mm system we have been using. Theoretically, the video projection will be for sources that are not available on film -- student stuff, "alternative" programming, multimedia productions and the like.

I have not been given any details so far other than hearing that the system will be using "stacked Barcos." This sounds very scary. Are dual projection stacks still necessary? I mean, to fill a 22ft high screen at presumably 4:3 or even 16:9 ratio, can't we get a picture bright enough using today's level of video technology with a single projector rather than needing to stack two? I am assuming that the only reason to stack is to get more light on the screen. Wouldn't a single unit be much more preferred than all the headaches that will be incurred using two?

This is just a preliminary question and I realize that I need a lot more information about the projector models they intend to stack, but in general terms, wouldn't it be better NOT to stack projectors but to specify one unit that will properly do the job? I am assuming that there will be the usual parallax and registration problems using two, especially since these things will not be in a permanent install -- they need to be moved to the projection tower and retrieved and placed in storage every summer.

I will try to get more information as to what Barco's are being contemplated and who and why stacking was suggested.

Posted by Richard Fowler (Member # 893) on 09-10-2007, 10:55 AM:

Most Barco chassis have very good stacking points. With stacking you always have a "backup". Projector aiming and internal lens shift make parallex almost nil, especially for your throw....you will probably have more issues with color correction, contrast and light evenness between the units to yield your final image. I have done stacks of 2 and 3 and I use a video test generator with multiple patterns and color bars for set up.

Posted by Paul Mayer (Member # 355) on 09-10-2007, 06:32 PM:

Indeed it depends on which Barco model we're talking about. As Richard mentioned stacking LCD machines is not that difficult - in fact they're much easier and faster than the old CRTs were.

For example, the last Super Bowl we did before the NFL shut us down at the Brenden Palms was done with pairs of stacked Sanyos. At the time the brightest machine we could get from Encore Productions had 5000 lumen output and we needed about double that. So we did stacks and they worked just fine (that was for standard definition 4:3 video on 22x29' screens). Since the pictures were just standard def OTA broadcast video we used the Avia and Video Essentials DVDs for the test patterns during line up.

These days 10,000 lumen machines are readily available so that job could be done today without stacking. Still, stacking is nice even if only to have backups available.

A short old thread about doing overlays: Superimposing 2 Data Projector Images

Posted by Frank Angel (Member # 248) on 09-10-2007, 06:35 PM:

Thanks Richard. At least that's some good news, and eases my mind a bit (because if it is already a done deal that I will have to live with, at least I am not going to have to see fringing on the screen).

But still, I don't see the advantage or the reason for doing a stack when for about the same amount of money, a single projector would do the job just as well -- all except the backup issue, of course. But I am told that Barco reliability is quite good -- should I be worried about high failure risk to the point that it should come into play in the decision to either purchase a two 10,000 lumen projectors as opposed to purchasing one 20,000 lumen unit?

Posted by John Hawkinson (Member # 1135) on 09-10-2007, 08:58 PM:

I would tend to assume that having multiple projectors means that pixels are less distinct, which is an advantage. But that's just total speculation...

Osram says....just kidding!

--jhawk