# New Facility - question about how to use back wall



## MrsZ (Mar 21, 2010)

I am certain this post could belong under lots of forums. I chose this one as I am making decisions for a new high school performing arts center.

The plans include a permanent back wall. Can I use this back wall as a cyc? How would it be treated (as in chemically)? In the interest of multi-functioning, could a back wall be used to project movies on if the school wanted to use the space as a large "movie theater"? Currently the plans call for a 200" projection screen; however, I would rather spend the money on a cyc. Bottom line: Can I turn the back wall into a cyc which would function as a movie screen?

Any advice would be appreciated! Thank you!


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## mstaylor (Mar 21, 2010)

I would try to make it multifunctional. You could make the wall a cyc with a black curtain that can close in front of it. It is possible to make the cyc double as a projection screen but you would need to run that by your video contractor. It depends on throw distances and a host of other variables.


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## Morpheus (Mar 21, 2010)

MrsZ said:


> I am certain this post could belong under lots of forums. I chose this one as I am making decisions for a new high school performing arts center.
> 
> The plans include a permanent back wall. Can I use this back wall as a cyc? How would it be treated (as in chemically)? In the interest of multi-functioning, could a back wall be used to project movies on if the school wanted to use the space as a large "movie theater"? Currently the plans call for a 200" projection screen; however, I would rather spend the money on a cyc. Bottom line: Can I turn the back wall into a cyc which would function as a movie screen?
> 
> Any advice would be appreciated! Thank you!


The easiest way would be rig the cyc/movie screen at the back of the theatre. You DON'T want to project onto any uneven surface, such as a wall, unless it was perfectly smooth - the light will show any imperfections.

Now, the issue with projecting a movie onto a cyc at the back - unless you have people on the stage, you are projecting through all that open stage space, which affects luminosity, but could also be an aesthetic issue.


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## Footer (Mar 21, 2010)

I have worked in a few spaces that have "hard" cycs. Basicly, they drywall the back wall, making sure it is perfectly smooth. paint it white, either satin or flat, and you are set to go. 

The projection screen thing adds a bit of an issue. With projection screens you want as much light as possible to hit the wall and bounce back. Goo Systems is one company that makes a product that will do that. It will also give you a good cyc as well. 

I have also seen venues that strech muslin on their US wall do act as a cyc. Its not a bad way to go. It can make maintenance a bit of a pain because they get beat up easy and every scratch and dent show.


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## ptero (Mar 22, 2010)

We have a hard back wall/upstage wall in our theatre. We use it as cyc sometimes. With or w/o a scrim downstage. It is wet plaster and not at all appropriate for projection - unless the rough 'look' fits intentions, which it has now and then. 

One consideration for us is whether using it as a cyc disrupts actor/technician ability to crossover from side to side. For a large show keeping a path across is essential for backstage traffic. Some shows permit no crossover onstage. The other routes 'around' are slow and taken into account if necessary. 

With a tallish ground row or scenic treatment providing sightline protection, we have both lit it and maintained a crossover for many productions.


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## MrsZ (Mar 23, 2010)

Wow... This forum is amazing!

My thanks to each of you for your information and insight. I appreciate your ideas and advice.

Thank you!


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## museav (Mar 28, 2010)

Morpheus said:


> Now, the issue with projecting a movie onto a cyc at the back - unless you have people on the stage, you are projecting through all that open stage space, which affects luminosity, but could also be an aesthetic issue.


I'm not clear how projecting through open space would affect the "luminosity" or the brightness or quality of a projected image. However, having the screen upstage does put the screen further from the viewers, thus requiring a larger screen, and would necessitate front projection. You would also probably want some way to mask or delineate the 'screen' portion of the wall when used for projection.


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## venuetech (Mar 29, 2010)

I would rather have a screen
Yes you can use the US wall as a projection surface. but the reality is that, the wall is a prime storage area and just keeping it clear of tall flats and other objects would be a real chore. often you will have built scenery in front of it. keeping the wall in pristine condition will require constant vigilance, day by day, year after year.

In a high school time and time again there will be need to access the screen in very short order with a minimum fuss. the event is usually very short, but having to clear that wall of stored scenery each and every time would make for a big hassle. 

Best location for a screen is directly in front of a midstage traveler. that would give you the most flexibility


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## Morpheus (Mar 29, 2010)

museav said:


> I'm not clear how projecting through open space would affect the "luminosity" or the brightness or quality of a projected image. However, having the screen upstage does put the screen further from the viewers, thus requiring a larger screen, and would necessitate front projection. You would also probably want some way to mask or delineate the 'screen' portion of the wall when used for projection.


longer throw distance, more footcandles dropoff...
Basically, i got lazy and simplified a whole bunch of maths.


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## museav (Mar 29, 2010)

Morpheus said:


> longer throw distance, more footcandles dropoff...
> Basically, i got lazy and simplified a whole bunch of maths.


Light does not drop off with distance, the output of a light source is the same regardless of the distance from it. What changes is the area that output is spread across, however once you introduce lenses that area is no longer a single fixed relationship to the distance from the source. So the brightness of the image produced by a projector for an A x B sized image is the same regardless of how far the projector is from the screen, the brightness of the projected image only changes if the image size changes. So the brightness for a 200" diagonal screen is dependent on the screen size and not the distance the projector is from that screen.

The same concept applies to sound, the 6dB per doubling of distance for distance effect is not really due to the distance but rather due to the fact that when you double the listener distance from a fixed pattern source the same output is being spread over a four times larger area. Air absorption itself is actually a separate factor.

It should be noted that these are theoretical and that real world effects such as losses in different lenses, reflective surfaces, etc. can affect the actual results. For example, a long throw for a projector may result in some loss in image brightness but that would be due to losses from using a long throw lens that effectively reduce the projector output and not due to the increased throw distance itself.


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## mixmaster (Mar 29, 2010)

We have a hard upstage wall, plaster over brick I think. We keep it painted with flat white latex paint. We find we do it about once a year. It's a good job for a couple of my workstudy students before our seasons ramp up in the fall.
As a cyc, it works well enough, although there's no way to cross stage behind it w/o going out into the hall. We catch a little flack from shows that "require" the use of cyc, but when they find out that they can add 4 feet to their stage depth and gain the use of the US traveler (which is hung US of the cyc pipe) they always use the white wall. We don't even have a cyc for our big venue anymore. No more often than we use it a 20x40 cyc on a horseshoe pipe is expensive, and a pain in the butt. The wall is just there, paint it once a year and forget about it.

As a projection surface, it seems to work OK. I was talking with one of our IT guys, who told me about a wall paint that he was looking at for his home theater, that was specifically designed to be projected on, and I'm considering trying that for our next coat of paint. The only real problem that we have using the white wall as a projection surface is sightlines. We have a slightly wider seating area than the width of our proscenium which means that the outside seats in the first 10 rows can't see all the way to the back of the stage the entire width of the back wall. The top half of the balcony loses the top half of the back row also. For us it's not a problem, as we rarly open the balcony, and sightline issues only kill 20 or so seats out of the 500 on the floor, but it's worth checking your venue. 
It's also nice to be able to project images without having to rig a screen every time, or kill a batten with a permanently mounted screen that only gets used occasionally. Our smaller facility has a screen on a roller mounted just US of the 1st electric, that covers 3/4 of the width of the stage. It's to big, and permenantly wired, so we can't move it, but its so big and so far downstage that it only leaves about 10 feet of useful space. In that position anyone walking in front of the screen gets lit and casts shadows. I can hit the back wall from a projector hung on a pipe and not have that problem in the big theatre.
Matt


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