Community Theater Green Room Discussion Board: projected scenery

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stanberry12000
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Joined: 1/18/11
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Topic: projected scenery
Posted: 3/26/11 at 2:03pm

I would like to project the scenery for The Full Monty. Probably on a screen that will be 20' WIDE and 10 feet tall. Any ideas. Will Powerpoint work?

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vickifrank
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Posted: 3/26/11 at 5:34pm

Basically yes, you can use powerpoint through a computer linked projector. But there are a few other concerns....

1.) Aspect ratio. This is the width:height ratio of your screen. In your case its 2:1. More typically its 4:3 or 16:9 for most projectors.

2.) Is your projector strong enough? For 20' wide you need at least 5000 lumens with XGA resolution. I'm not an expert in this so this is based on a few rules-of-thumb.

3.)Front or rear projection? (See next question because distance upstage or downstage matters) Front projection can have actors casting shadows on the scenery. Rear projection has the difficulties of space and 'hot spotting'.

4.)Where do you locate the projector? (If you are projecting on a scrim you want a steep angle) For a normal projector you need to have the projector about 16 feet away to get the 20' wide image. For a short throw (wide angle lens) you need about 13 feet. For an ultrashort throw (special very wide angle) you need about 6 feet. If you have the projector, look up the throw distance to find out how big an image you can get at a certain distance. For rear projection you can shorten this distance up to a half with the use of a mirror--but be aware this requires some fiddle/experimentation time.

5.) What is your screen? If it is a screen that exists you can test some of the above now. If you don't have that screen then there are the scrim vs. screen questions (addressed and discussed in a recent post here) and the cost concerns.

Edited by vickifrank - 3/26/11 at 5:35pm

_____________

http://www.studio-productions-inc.com
1-800-359-2964

The theater scrim people

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David McCall
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Posted: 3/27/11 at 5:39pm

Here is an image to show the principal behind folding a projected image using mirrors. These drawings are based on a 30' throw yielding a 20' picture.

In the first set we are folding the image horizontally. Picture H-1 shows the normal horizontal cone. Picture H-2 is that same cone but it is folded very close to the screen to minimize the space needed behind the screen. I've added a second fold to reduce the width needed.

In the second set we have placed the mirrors vertically. Picture V-1 shows the normal vertical cone. Picture V-2 is that same cone but it is folded very close to the screen to minimize the space needed behind the screen. I've added a second fold to allow the projector to be mounted above (or below) the screen.

One thing you will notice is that the mirrors get pretty big if you want to cut the distance by much. Obviously the mirror can be smaller if you don't need to cut the distance as much. You can use any combination of horizontal and vertical folds.

An easy way to play with your ideas is to make a triangular piece of paper that is the right scale for the projected distance and screen size. I use graph paper. You can then fold the triangle any way you want to see how your folded beam is going to work. Traditionally you try to keep the folds at a 45 degree angle from the beam's center line. If you use first surface mirrors this becomes less important.

Big glass mirrors are going to cost a lot of money especially first surface mirrors. Rosco (the gel and paint folks) make a heat shrinkable mylar mirror that works pretty well if you do it right. You need a fairly rigid and very flat frame to stretch the mylar on. You don't want the mylar to touch anywhere except at the edges. Then you shrink it with a heat gun or hair dryer. I'm not sure how big you can make it using that material.

David M

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vickifrank
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Posted: 3/27/11 at 8:25pm

Nice diagrams, David. I have people ask all the time regarding mirrors and projection, usually, I simply tell them to allow 'fiddle time' to get it right--I'm going to direct them to this thread just to look at the diagrams and your discussion on the technique. Thanks for sharing this, this discussion will help a lot of folks!

_____________

http://www.studio-productions-inc.com
1-800-359-2964

The theater scrim people

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JoeMc
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Location: Australia
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Posts: 832

Posted: 3/30/11 at 11:25pm

G'donya David your diagram's are great!

Like others I normally mess about tweaking, for hours, with the mirror to bounce the light & adjust masking to suit [1:15].

Since I did 'A Chorus Line' I have been using the Rosco heat shrink mirror film which is much easier than muckin'about with glass mirrors & to produce the mirror size required.

http://www.rosco.com/us/technotes/designer/data_sm.cfm

A thing I remember as a young bloke back in the 1950"s was sets projected on the cyc, especially for Opera. Which gave a 3 dimensional set piece, such as a flying horse or greek columns.

It was accomplished via two slide projectors positioned on the first fly floors & the image projected on the cyc, I must admit it did look realistic.

Aparently it was produced by taking photographs of a detailed stage model setting from two positions & then producing slide transparencies. They then duplicated the slide projectors to be placed in the same measured positions on stage, as were photographed on the model.

I forgotten the name of the bod [A germanic name I think?] that devised this method, but it was a fantastic effect.

Edited by JoeMc - 3/31/11 at 12:21am

[western] Gondawandaland
"Hear the light & see the sound!
TOI TOI CHOOKAS
{may you always play to a full house!}

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museav
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Joined: 11/06/09
Location: United States
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Posts: 38

Posted: 4/23/11 at 12:40pm

Just be aware that mirrors do incur some loss or brightness, can introduce optical aberrations and if glass, need to be first surface (the silvering on the face rather than the back). One common difficulty can be how you mount them and provide sufficient ability to accommodate any required adjustments. Also, keep in mind that you can use mirrors vertically or horizontally.

Some other potential considerations:

The lens can effect the brightness and allowable projector position. A very long throw lens may have greater optical loss. A very short throw lens may require that the projector be on both the horizontal and vertical centerline of the projected image.
Ambient light on the projection surface limits the black levels and image contrast possible. You cannot easily make up for an increased black level, however maintaining usable contrast with greater ambient light on the screen means using higher output projectors.
As mentioned, think about format or the relationship of the width and height of the image. Projectors are commonly 4:3, 16:9 or 16:10 format. They can display images of various formats via letterboxing or pillarboxing but remember that the projector brightness is based on the overall area the projector is producing and not just the area occupied by the image. So if an image does not occupy the full potential area then it also only represents a portion of the projector output. A common example, if you letterbox a 16:9 format image on a 4:3 format projector then you are using only 75% of the actual projected height for the image itself, and thus the image also represents only 75% of the projector brightness.

The reality is that projecting general backdrops typically requires a large amount of physical space for the projectors and projection path and either very bright, and thus expensive, projectors or multiple projectors edge blended together to form one image.

Brad W.

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Set Design and Construction
Community Theater Green Room Discussion Board :Producing Theater :Set Design and Construction

Author	Message
stanberry12000 Walk-On Joined: 1/18/11 Location: United States Online Status: Offline Posts: 0	Topic: projected scenery Posted: 3/26/11 at 2:03pm
	I would like to project the scenery for The Full Monty. Probably on a screen that will be 20' WIDE and 10 feet tall. Any ideas. Will Powerpoint work?

	IP Logged

vickifrank Celebrity Joined: 9/21/07 Location: United States Online Status: Offline Posts: 332	Posted: 3/26/11 at 5:34pm
	Basically yes, you can use powerpoint through a computer linked projector. But there are a few other concerns.... 1.) Aspect ratio. This is the width:height ratio of your screen. In your case its 2:1. More typically its 4:3 or 16:9 for most projectors. 2.) Is your projector strong enough? For 20' wide you need at least 5000 lumens with XGA resolution. I'm not an expert in this so this is based on a few rules-of-thumb. 3.)Front or rear projection? (See next question because distance upstage or downstage matters) Front projection can have actors casting shadows on the scenery. Rear projection has the difficulties of space and 'hot spotting'. 4.)Where do you locate the projector? (If you are projecting on a scrim you want a steep angle) For a normal projector you need to have the projector about 16 feet away to get the 20' wide image. For a short throw (wide angle lens) you need about 13 feet. For an ultrashort throw (special very wide angle) you need about 6 feet. If you have the projector, look up the throw distance to find out how big an image you can get at a certain distance. For rear projection you can shorten this distance up to a half with the use of a mirror--but be aware this requires some fiddle/experimentation time. 5.) What is your screen? If it is a screen that exists you can test some of the above now. If you don't have that screen then there are the scrim vs. screen questions (addressed and discussed in a recent post here) and the cost concerns. Edited by vickifrank - 3/26/11 at 5:35pm
	_____________ http://www.studio-productions-inc.com 1-800-359-2964 The theater scrim people
	IP Logged

David McCall Celebrity Joined: 1/28/09 Location: United States Online Status: Offline Posts: 299	Posted: 3/27/11 at 5:39pm
	Here is an image to show the principal behind folding a projected image using mirrors. These drawings are based on a 30' throw yielding a 20' picture. In the first set we are folding the image horizontally. Picture H-1 shows the normal horizontal cone. Picture H-2 is that same cone but it is folded very close to the screen to minimize the space needed behind the screen. I've added a second fold to reduce the width needed. In the second set we have placed the mirrors vertically. Picture V-1 shows the normal vertical cone. Picture V-2 is that same cone but it is folded very close to the screen to minimize the space needed behind the screen. I've added a second fold to allow the projector to be mounted above (or below) the screen. One thing you will notice is that the mirrors get pretty big if you want to cut the distance by much. Obviously the mirror can be smaller if you don't need to cut the distance as much. You can use any combination of horizontal and vertical folds. An easy way to play with your ideas is to make a triangular piece of paper that is the right scale for the projected distance and screen size. I use graph paper. You can then fold the triangle any way you want to see how your folded beam is going to work. Traditionally you try to keep the folds at a 45 degree angle from the beam's center line. If you use first surface mirrors this becomes less important. Big glass mirrors are going to cost a lot of money especially first surface mirrors. Rosco (the gel and paint folks) make a heat shrinkable mylar mirror that works pretty well if you do it right. You need a fairly rigid and very flat frame to stretch the mylar on. You don't want the mylar to touch anywhere except at the edges. Then you shrink it with a heat gun or hair dryer. I'm not sure how big you can make it using that material.
	David M
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vickifrank Celebrity Joined: 9/21/07 Location: United States Online Status: Offline Posts: 332	Posted: 3/27/11 at 8:25pm
	Nice diagrams, David. I have people ask all the time regarding mirrors and projection, usually, I simply tell them to allow 'fiddle time' to get it right--I'm going to direct them to this thread just to look at the diagrams and your discussion on the technique. Thanks for sharing this, this discussion will help a lot of folks!
	_____________ http://www.studio-productions-inc.com 1-800-359-2964 The theater scrim people
	IP Logged

JoeMc Celebrity Joined: 3/13/06 Location: Australia Online Status: Offline Posts: 832	Posted: 3/30/11 at 11:25pm
	G'donya David your diagram's are great! Like others I normally mess about tweaking, for hours, with the mirror to bounce the light & adjust masking to suit [1:15]. Since I did 'A Chorus Line' I have been using the Rosco heat shrink mirror film which is much easier than muckin'about with glass mirrors & to produce the mirror size required. http://www.rosco.com/us/technotes/designer/data_sm.cfm A thing I remember as a young bloke back in the 1950"s was sets projected on the cyc, especially for Opera. Which gave a 3 dimensional set piece, such as a flying horse or greek columns. It was accomplished via two slide projectors positioned on the first fly floors & the image projected on the cyc, I must admit it did look realistic. Aparently it was produced by taking photographs of a detailed stage model setting from two positions & then producing slide transparencies. They then duplicated the slide projectors to be placed in the same measured positions on stage, as were photographed on the model. I forgotten the name of the bod [A germanic name I think?] that devised this method, but it was a fantastic effect. Edited by JoeMc - 3/31/11 at 12:21am
	[western] Gondawandaland "Hear the light & see the sound! TOI TOI CHOOKAS {may you always play to a full house!}
	IP Logged

museav Lead Joined: 11/06/09 Location: United States Online Status: Offline Posts: 38	Posted: 4/23/11 at 12:40pm
	Just be aware that mirrors do incur some loss or brightness, can introduce optical aberrations and if glass, need to be first surface (the silvering on the face rather than the back). One common difficulty can be how you mount them and provide sufficient ability to accommodate any required adjustments. Also, keep in mind that you can use mirrors vertically or horizontally. Some other potential considerations: The lens can effect the brightness and allowable projector position. A very long throw lens may have greater optical loss. A very short throw lens may require that the projector be on both the horizontal and vertical centerline of the projected image. Ambient light on the projection surface limits the black levels and image contrast possible. You cannot easily make up for an increased black level, however maintaining usable contrast with greater ambient light on the screen means using higher output projectors. As mentioned, think about format or the relationship of the width and height of the image. Projectors are commonly 4:3, 16:9 or 16:10 format. They can display images of various formats via letterboxing or pillarboxing but remember that the projector brightness is based on the overall area the projector is producing and not just the area occupied by the image. So if an image does not occupy the full potential area then it also only represents a portion of the projector output. A common example, if you letterbox a 16:9 format image on a 4:3 format projector then you are using only 75% of the actual projected height for the image itself, and thus the image also represents only 75% of the projector brightness. The reality is that projecting general backdrops typically requires a large amount of physical space for the projectors and projection path and either very bright, and thus expensive, projectors or multiple projectors edge blended together to form one image.
	Brad W.
	IP Logged