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Projector Behind the Screen

Scott Wilkinson  |  Apr 25, 2012

I have designed and framed out a dedicated home theater with a separate room for a projector to project the image onto a translucent screen to be viewed in the theater room. I spoke with both projector and screen manufacturers before construction, and I asked them which would produce a better image—traditional front projection or rear projection such as I have in mind. The answer was unanimous: rear projection would produce a better image. I realize that the market for this type of setup is much smaller than traditional front-projection because of the obvious design considerations. But there are many advantages over front-projection, primarily and most importantly a better picture as well as no projector noise or heat in the viewing area. I would love to see some discussion on this type of projection in the magazine.

Duane Clemens

You make some good points here. The market for a rear-projection system (as opposed to an all-in-one rear-projection TV) is very small because such a system is very expensive. Not only does it require a second room dedicated to the projector (with extra cooling to handle the heat), but the screen must be built into a wall, which is much more involved than hanging a front-projection screen. Also, good rear-projection screen material for such a system ain't cheap—for example, a 96x54-inch piece of Stewart StarGlas 60 with anti-reflective coating and Quickstall frame will set you back $10,660, more than three times as much as a front-projection screen of the same size.

You're also correct that such a rear-projection system offers several advantages over front projection. Aside from eliminating the projector's noise and heat from the viewing room, you needn't worry about walking in front of the projector and casting a shadow on the picture. And depending on how bright the projector is, this type of system can stand up to some amount of ambient light and still look good—it's sort of like a giant flat-panel TV. You can even install such a system so the viewing area is outdoors (as seen in the photo above), while the projector is protected in its own room.

However, I'm not sure I agree that the picture quality is inherently better than a front-projection system. If the screen material is not top-notch, you could see hot-spotting (which is a potential problem with front-projection screens as well). Granted, with a good screen, the image quality of a rear-projection system is likely to be better than front projection in the presence of some ambient light, but in a dark room, I wouldn't say one is necessarily better than the other.

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COMMENTS
ht-vince's picture
Submitted by ht-vince on April 25, 2012 - 1:37pm

I have understood that the room behind the screen must be nearly as deep as a front projection room (barring some radical anamorphic solution) but most interesting to me when I considered it is that optimally it should be blacked out. For the same reasons that reflections are issues on front projection systems. This put me off and took the conventional route.

Vince

Scott Wilkinson's picture
Submitted by Scott Wilkinson on April 25, 2012 - 3:48pm
You're entirely correct that the dedicated projector room should be totally blacked out to obtain the best picture quality. And unless you get a so-called ultra-short-throw projector, the throw distance will have to be pretty long. That's a lot of space in a home that can't be used for anything else but housing the projector, which means it's for rich folks only.
utopianemo's picture
Submitted by utopianemo on April 26, 2012 - 6:10am

I know this is off the main topic, but I'm surprised short-throw projectors haven't been more developed as a viable HT format. I know there are some challenges that need to be overcome, but that didn't stop LCD technology, did it?

Short-throw PJs offer some inherent advantages over traditional front projectors. Blocking the projector is mostly a non-issue, and more importantly, the lamp doesn't need to be nearly as powerful. Aside from an energy savings, this means it can be easier to fill a large screen.

Moreover, placing the projector that close can open up new possibilities. I saw an experiment where a DIYer placed a standard projector extremely close to a black wall. Although the "screen material" was exactly the opposite color one would expect to use in a projection environment, the whites still came out very white. The contrast ratio went through the roof! It gave me an idea of what is possible when distance is a lesser factor in the overall projection equation.

jnemesh's picture
Submitted by jnemesh on April 26, 2012 - 9:43am

There are several companies making rigs where you mount your projector in a cavity and have it shooting vertically at a mirror that then reflects the image to the back of your screen. These are a little more elaborate to set up, but they DRAMATICALLY reduce the amount of space needed behind the screen!

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