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Lights and Sound
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Quote mvp1114 Replybullet Topic: Evita
    Posted: 11/22/12 at 10:29am
"your reach should exceed your grasp" is our Director's motto, I think.  I've been informed we're doing "Evita" this spring, and I'm looking for suggestions on what to use for some of the "projection" bits.
We have an OLD proscenium stage (1912) with a fairly decent lighting rebuild and control, but I'm trying to figure out what and where to mount a projector.  I have a couple of options, but what kind of projector can stand up to full stage lighting?  Yes, I know not to light the area where the projection screen is but seriously, we've had projections several times before and I've never been satisfied as it usually looks washed out.
This is a complicated enough show that I think the projections add to the audience's understanding.  PLUS I can get some external help on assembling the projection stock, SO:
1) mounted to the electricals above stage - our problem is that it's CROWDED up there - old shallow stage, and while I can put a white scrim fairly far back, I haven't been able to get a tight enough focus that way before.  It looks a little "sfumato" if you know what I mean
2) projected from the pit - better focus, but it washes out shooting thru the rest of the lighting and it's a distraction I think for the audience - PLUS, this is a huge pit orchestra so room would be an issue
3) projected from tech area - again, I'd be worrying about washout but my projector isn't really desgned for that long of a shot - any suggestions on a long projector that can be rented, that we can hook up to a computer?  School budget here, remember.
4) projected from balcony/above audience/etc - just not an option the way we're set up.  Balcony and long throw spot locations are just too high to hit the projection area well, and ceiling is a 60+ foot inacessible area
Ideas?  Thanks!
schlechy techy
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David McCall

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Quote David McCall Replybullet Posted: 11/22/12 at 4:57pm
I've seen Projectors hanging from the front edge of the balcony.
We use a projector that is at the top of the light booth window (pretty much even with the top of the proscenium). It is about 6000 lumens and produces a good looking 35' x 17' picture in the dark. The more light you put on the stage the more washed out it becomes. Side light causes less damage than front or top light. Flat black floor is much better than shiny oak.
We project backgrounds for plays, musicals and even assembles all of the time. We try to keep light under control as much as the scene will allow and a lot of people seem pretty happy with the result.
I'd love to have a 12,000+ lumen high definition projector that would produce a 50' wide image at 130'.
David M
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Quote vickifrank Replybullet Posted: 11/23/12 at 8:42am
Point #1:

When projecting on a scrim you should project from an angle, because a scrim is basically a fabric with voids or holes in it.  You get a better projection from an angle (from top, bottom, left or right) because less light goes through the voids or holes.  You also avoid some hotspotting in rear projection.  You correct the image with the keystone adjustment to square it.

Its a little interesting, because everyone knows that you light a scrim from an angle (think cyc lighting), and they naturally shine gobos from an angle, but don't realize that you project from an angle.

The following suggestion require Chameleon Scrim (because you should never rear-project on sharkstooth--its does very poorly for rear projection.  Chameleon is a good front and rear projection scrim.  Chameleon is better for projection because it has smaller holes and --as a synthetic--it is a more reactive surface for projection--both reflecting and transmitting light through it better.).

Point #2:

Consider rear projecting (on Chameleon) with your short-throw projector, from the wings or above or below with the projector behind a ground row.  Also consider doing what you can do with Chameleon only--tilt the scrim vertically toward the audience.  So hang the scrim on the batton, but pull the lower pipe weight upstage of that batton.  This effectively tilts the scrim away from the downstage stage lighting so you don't wash out the projection. Again, this is Chameleon only.  Doing this with sharkstooth wouldn't work because sharkstooth needs to be stretched, not just anchored.

Point #3:

About 'throw':  You can have long throw, short throw and ultra short throw projectors.  Throw is the distance the projector is away from the screen.  You can modify a long throw projector to short throw by buying a short throw lens, but usually don't go the other way.  I wouldn't suggest taking your projector back a distance beyond what it was designed for because it will become too faded.  This is because light levels quickly drop off the further back you go.  So you need a higher lumen projector to use for a long throw projection. (Light levels drop at the cube of the distance from a pinpoint light source if I remember my physics right, but in the case of projection a lens is involved and I'd guess you lose focused light at the square of the distance as an approximation)

So where you've gotten a faded projection before, the three basic causes are:

1.) stage light hit the scrim/screen and faded the projection (like turning house lights on in a movie theater).

2.) A scrim has holes in it, so light is lost unless you project from an angle. 

3.) The projector was wrong-sized for the throw (so you need a bigger lumen projector, or a shorter throw).

If you remedy one or more of those you will get better results. 

Also short-throw projectors save you money by being smaller lumens.  If you can go with an ultra short throw the projector is much smaller and cheaper--imagine how much smaller a flashlight needs to be if it is to be seen at 25 feet than 130 feet!  Same for a projector.

Finally, for still shots and for liveaction with some special software, two smaller projectors can be coordinated to save you money.  Image one in the SR wings and the other in the SL wings and blending the image center stage.

Edited by vickifrank - 11/23/12 at 9:08am

The theater scrim people
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Quote museav Replybullet Posted: 11/25/12 at 6:52am
I think there may be a basic misunderstanding here.  Ignoring details such as losses through the actual optics, the image brightness is a function of the image size, not the throw distance.
If you have a fixed lens the projected image brightness does indeed drop as the throw distance increases, however that is because the image area over which the projector output is spread is also increasing.  In comparison, with zoom lenses there is no longer a direct relationship of image size to throw distance, and thus of image brightness to throw distance.  If you have X lumens over a A' by B' image then it does not really matter if the projector is 10' away or 100' away, either situation is the same projector output over the same image area and thus the same image brightness.
You can also look at this the other way.  Pick a throw distance, then adjust the projector zoom and as a result the image size changes.  Same projector and thus the same light output, but over a varying image area and thus a varying image brightness.  It is the area over which the light from the projector is spread and not the distance from projector to screen that matters.
On a lesser note, be wary of assumptions regarding where a projector can or should be located, different projectors and even different lenses on a projector may have different requirements in terms of where the projector should be located relative to the projected image and also in how much compensation the projector and lens can accommodate if not in the ideal location.
Going back to the OP, consider this.  One factor for the projected image is the image brightness or how bright white can be.  However another factor is how dark black is in the image.  The difference between those is the image contrast and insufficient contrast is what relates to an image being 'washed out'.  You can try to improve the projected image contrast by increasing the white level by using a brighter projector but you can only go so far before that is impractical or plain difficult to view.  In most cases the better approach is to try to reduce the black level, which is generally controlled by the ambient lighting on the projection surface.
Rear projection if often a good alternative, however it does require a proper screen surface and sufficient space behind the screen.  You can shorten that distance with very short throw lenses, however such lenses often have tradeoffs in terms of hotspotting and in where the projector must be located and how much that can vary.  Mirror systems can also be used to 'bend' the light path reduce the physical depth required but add cost and require that nothing else be in the 'folded' light path.
For front projection do not worry too much about the distance to the projector or projecting through other lights in terms of the image brightness.  To be technically accurate, long throw lenses due typically result in a bit less output from the projector but that is due primarily to losses within the additional elements in the lens.  But, if you have a projector that can be used with different lenses or for which an extender is available then you may be able to get appropriate optics to allow the projector to be further away such as in the Tech Booth.  Of course that may create other issues regarding noise, heat and power in the tech booth, but it may at least allow that option.
Brad W.
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