Backprojection Question
By man1 - usenet poster
Just handed a set sketch calling for "four back-projection screens which
will also be used for front projection. Two must be see-through so actor
can be seen when lit behind it."
Would appreciate any tips on type of material you've found successful for
such screening.
Thanks,
John Wesley Brett
AABCTheater
Best Solution
posted on Aug 02, 2007
Powe33 - usenet poster
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Theatre guy turned AV guy delurking:
Da-Lite makes a screen surface for standard Fastfold screen frames that is a
compromise between front and rear surfaces. (ie: it dosen't do either as
well as a strictly front or rear surface, but is reflective enough for front
and translucent enough for rear.) IIRC they call it a "Dual View" surface.
As another poster said, it is a creamy off-white color. With sufficently
powerful projectors, this might solve part of your problem.
IMHO the requirement for a reflective / translucent / transparent screen
can't be done with one unit. To be transparent, you need a scrim or
something, which *might* work for front projection but not rear, you'll
blind the audience with the projection. I'd look for a way to use the "Dual
View" screens and switch them for a scrim for the transparent
bits...hopefully these can be transitions from front projection to see-thru!
Use a dense scrim and you might be ok...but even a dense scrim will be too
transparent for rear projection. I feel for you...you are being asked to
solve an apples / oranges / mangoes problem!
No matter what...you need big, powerful projectors, and a way to substitute
the "Dual View" screens for a scrim when you need the transparent effect!
HTH...Best of luck!
Feel free to e-mail questions...remove obvious spam-trap.
John Lauer
Seattle,WA
Da-Lite makes a screen surface for standard Fastfold screen frames that is a
compromise between front and rear surfaces. (ie: it dosen't do either as
well as a strictly front or rear surface, but is reflective enough for front
and translucent enough for rear.) IIRC they call it a "Dual View" surface.
As another poster said, it is a creamy off-white color. With sufficently
powerful projectors, this might solve part of your problem.
IMHO the requirement for a reflective / translucent / transparent screen
can't be done with one unit. To be transparent, you need a scrim or
something, which *might* work for front projection but not rear, you'll
blind the audience with the projection. I'd look for a way to use the "Dual
View" screens and switch them for a scrim for the transparent
bits...hopefully these can be transitions from front projection to see-thru!
Use a dense scrim and you might be ok...but even a dense scrim will be too
transparent for rear projection. I feel for you...you are being asked to
solve an apples / oranges / mangoes problem!
No matter what...you need big, powerful projectors, and a way to substitute
the "Dual View" screens for a scrim when you need the transparent effect!
HTH...Best of luck!
Feel free to e-mail questions...remove obvious spam-trap.
John Lauer
Seattle,WA
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Solution #2
posted on Aug 02, 2007
Cato - usenet poster
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My sincerest appreciate for all you thoughts and recommendations (including
what the designer is drinking).
This morning, I'm taking the comments to him and hopefully will get a new
"drawing board."
Since he wants four of them...I'll recommend he split the effects between
them.
I've racked my brain on this one for days and glad to see I'm not crazy
despite my relatively small career in community theatre.
Again thanks for you help.
John Wesley Brett
AABC Theatre
what the designer is drinking).
This morning, I'm taking the comments to him and hopefully will get a new
"drawing board."
Since he wants four of them...I'll recommend he split the effects between
them.
I've racked my brain on this one for days and glad to see I'm not crazy
despite my relatively small career in community theatre.
Again thanks for you help.
John Wesley Brett
AABC Theatre
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Solution #4
posted on Aug 02, 2007
Bouncy - usenet poster
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You have a set of basically incompatible requirements. For the see through
ones I'd use some scrim material and drop the ambient light level in front of
the screen as low as possible when doing the rear projection. When doing
front projection, roll down some standard front projection screen material
behind the scrim during a blackout. For the other ones, use rear projection
screen material instead of scrim. If you have to match brightness levels,
then
use scrim on all four.
The front projection screen material needs to be touching the back of the
scrim material, and wrinkles will *really* show up in the scrim material.
THis is going to give you poor to adequate front projection performance,
crappy rear projection performance, and normal see through performance.
You will need brighter projectors to compensate for the poor performance of
the scrim material.
Maybe you could have three coverings, a scrim, FP, and RP material, and
switch the coverings during blackouts. You could go tell the designer that
what s/he wants is very expensive, and to go fight for the budget themselves
as you are not going to do that without the budget committed. Then go buy
or rent ten fast-fold screens of the appropriate size and type, and rig some
sort of track or fly system for each screen.
--Dale
ones I'd use some scrim material and drop the ambient light level in front of
the screen as low as possible when doing the rear projection. When doing
front projection, roll down some standard front projection screen material
behind the scrim during a blackout. For the other ones, use rear projection
screen material instead of scrim. If you have to match brightness levels,
then
use scrim on all four.
The front projection screen material needs to be touching the back of the
scrim material, and wrinkles will *really* show up in the scrim material.
THis is going to give you poor to adequate front projection performance,
crappy rear projection performance, and normal see through performance.
You will need brighter projectors to compensate for the poor performance of
the scrim material.
Maybe you could have three coverings, a scrim, FP, and RP material, and
switch the coverings during blackouts. You could go tell the designer that
what s/he wants is very expensive, and to go fight for the budget themselves
as you are not going to do that without the budget committed. Then go buy
or rent ten fast-fold screens of the appropriate size and type, and rig some
sort of track or fly system for each screen.
--Dale
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Solution #5
posted on Aug 02, 2007
Phoebe - usenet poster
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I used to have a cream BP screen (they have much wider viewing angles
than dark ones) which was excellent for FP, but I'd agree with Gareth
that Transparency with a projections screen is impossible. If a screen is
transparent enough to see an actor through, then you will get a very dim
projection image, and worse, a second image on what ever surfaces are
behind the screen (FP) or dazzling of the audience (BP)
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Solution #6
posted on Aug 02, 2007
Green1 - usenet poster
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Generally, projection material is for either front or back projection. A
mixture of FP and BP onto the same screen is going to require a compromise
somewhere along the line, as you won't get good results from both using the
same material.
Also, don't expect to be able to see a lit actor standing upstage of the
screen - projection screens, by necessity, are fairly opaque (BP screens
less so than FP screens). If the requirement was a dissolve effect and
EITHER front OR back projection, I'd suggest having a screen which could be
slid/flown/whatever out of the way, with a gauze behind it (if front
projecting) or in front of it (if back projecting) which could then be used
for the dissolve. But to front project, back project and dissolve all using
the same screen sounds to me like a pretty impossible task.
--
G A R E T H H U G H E S -
Production Lighting Services
--
Remove the obvious spam trap from the "reply-to" address to e-mail me
mixture of FP and BP onto the same screen is going to require a compromise
somewhere along the line, as you won't get good results from both using the
same material.
Also, don't expect to be able to see a lit actor standing upstage of the
screen - projection screens, by necessity, are fairly opaque (BP screens
less so than FP screens). If the requirement was a dissolve effect and
EITHER front OR back projection, I'd suggest having a screen which could be
slid/flown/whatever out of the way, with a gauze behind it (if front
projecting) or in front of it (if back projecting) which could then be used
for the dissolve. But to front project, back project and dissolve all using
the same screen sounds to me like a pretty impossible task.
--
G A R E T H H U G H E S -
Production Lighting Services
--
Remove the obvious spam trap from the "reply-to" address to e-mail me
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