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Topic: Mobile rear projection setup for auditorium
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Joined: Mar 16, 2014
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Hi chaps, we are just about to invest in a bit of a unique rear projection set-up and I would be interested in any opinions on our choice of equipment.

Basically we have been asked to design a rear projection set-up that can be easily transported and used in medium-ambient light such as small indoor arenas (windows at roof level, typically about 30m from screen to audience in an arc of about 170 degrees.

We're in a poor country so big ticket projectors are out of the question and many of the locations are not served by paved roads so any glass - screens, mirrors etc - are not practical.

We are thinking of going for a custom rear projection box with this projector http://www.projectorcentral.com/EIKI-LC-XL200AL.htm matched to the short throw 0.8 lens. That would make it about $5000 plus a Da-Lite DaTex High contrast screen around 100-120inches diagonal, around $600. We could transport it easily and set it up really quickly in each new location.

Does that sound reasonable? Any better ideas out there?
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Joined: Mar 28, 2005
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It is strongly recommended that you get black drapery to cover the space between the projector and the back of the screen. This will significantly improve the image on the front side of the screen and should only be a couple hundred dollar addition to the setup.

I would possibly talk to Draper, Dalite, etc. to see how many lumens they recommend per square foot if you have a black covered rear projection space with short throw projector vs. an open space. I would think that you could possibly get away with something like this instead:
http://www.projectorcentral.com/Vivitek-D873ST-projection-calculator-pro.htm

You could pick up TWO of those projectors, coverings to black out the rear projection space, and the screen and still come out well ahead, and likely deliver a better overall image at 120" diagonal compared to a non-covered rear projection space and a 6,000 lumen projector.

Your screen size really doesn't demand a ton of lumens, and while the lumens certainly do help, it is the rear projection in a dark space which can really set things apart. An unfortunate lack of lower priced bright rear projection does introduce some choice considerations in all of this.

Keep in mind that you are looking at a 1024x768 projector which really doesn't match up with all the widescreen laptops and video presentations of today, which can impact your setup a lot.

As a consideration for widescreen, this model is 6,000 lumens and offers a 1.0 throw ratio (with some zoom flexibility) for under $5,000...
http://www.projectorcentral.com/Optoma-TW865-NL-projection-calculator-pro.htm

This one is a bit less:
http://www.projectorcentral.com/Sharp-XG-PH80WN-projection-calculator-pro.htm

Both models are 1280x800 resolution, which puts up about a million pixels on screen vs. 3/4 of a million with XGA, but more importantly, those pixels will be more heavily used with widescreen content. So, a 16:9 HD video on a 1280x800 screen will use about a million pixels, and the full brightness available and screen size, while the same film will only use about half a million pixels of a 1024x768 projection image. (1024x576) The effective brightness will be lower, or the screen size will be lower, or both.

If I wanted short throw, and could get away with a 100" diagonal, and a widescreen image, then this would be way up on the potential list:
http://www.projectorcentral.com/NEC-NP-M352WS.htm

It will throw a 100" diagonal from 3'5" and put up over 100 lumens on screen. This minimizes the distance behind the screen, allows easier addition of a black cover, and should be plenty bright for the viewing audience.
AV Integrated - Theater, whole house audio, and technology consultation during the build and installation process in the Washington, DC metropolitan area.
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Joined: Mar 16, 2014
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Wow, thank you for such a comprehensive and researched reply, appreciate it. Your advice about the projector box is well noted, it is something we have already factored in, it seems the most cost effective way of increasing brightness.

You are absolutely right about the 4:3/16:9 issue. The reason I hadn't gone with 16:9 was that I hadn't found a setup which was short throw and 6000 lumens. Stacking is possible but the idea of having to make the adjustments in each new place is scary, although I have seen the possibility of storing the settings.

Having spoken with Da-Lite who suggested at least 4000 lumens in a projector box, and ProDisplay who suggested 6000 I am looking harder at the 16:10 version of the EIKI. It has 5500 lumens, but I assume that is purely down to the wide resolution rather than any change in output, and realistically it is probably putting more lumens on the screen than the 4:3 at 16:9.

I am aiming higher with the brightness due to the variable nature of the auditoriums we will be using. I'd rather be safe than regret it after.

When I get some equipment in I will post back with some observations.