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Rear screen projection as a light source


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#1 Michael Rizzi

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Posted 05 December 2006 - 09:56 PM

Hello,

I will be shooting a music video on HD where the band is playing in a "room" essentially made from 4 walls that are screens with projected moving images on them, the room will most likely be 15-20 feet square and 10 feet high (depending on our screens). The director would ideally like the only light to be coming from the walls and maybe a few practicals inside the room. The set will be dressed like a living room (couches, chairs, coffee table, lamps, etc.) so there's room for motivated practicals. My questions are: 1. What strength of projector would I need to successfully project an image and have enough light pass through the screen to light the subjects? 2. What kind of screen material would be best suited for this type of application? I was thinking even using a silk or 1/4 grid or china silk or something if the actual rear screen projector screens are too thick.
3. If the screens do not provide enough light, what would be some methods of using artificial lighting (besides practicals) to light the inside of the room without spilling onto the screens from the inside.

Any ideas would be appreciated. Thank you.

Rizzi
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#2 Bernhard Zitz

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Posted 06 December 2006 - 06:29 AM

2. What kind of screen material would be best suited for this type of application? I was thinking even using a silk or 1/4 grid or china silk or something if the actual rear screen projector screens are too thick.

For rear-projection on a window I had very bright, good results with lime-paper (what architects use to draw on), don't know if this exists in the size of a living-room. Frost gel does the job as well, rolls from lee filters are 7.62m x 1.22 m, maybe not large enough, and hard to mount really flat.
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#3 Adam Frisch FSF

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Posted 10 December 2006 - 02:10 PM

Just come off such a job:

We had a massive 10000 ANSI lumens professional projector that projected onto a gauze (half transparent) and I just barely got it with 200ASA speed film and with T1.3 lenses shooting wide open an one a prayer.

Obviously, if you have a HD camera, that is closer to 400ASA in sensitivity. But the lenses are slower, so you probably end up roughly in the same place. But a better reflecting screen (or transmitting in this case), should probably wrangle another couple of stops out of it. Should be fine even with a smaller projector - we had quite a big projection at about 20ft across.
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