using video projectors on stage

[JMackenzie]

Hi.

I have been using a video projector mounted on a fixed lighting bar to create some scenery effects. It is mounted fairly high, and has enough keystone adjustment to have a proper image. My problem is that the image size is not big enough to fill the back wall, which is painted white for the whole width of the stage. I cant mount it any further away because there is nothing to fix it to without some serious modifications to the ceiling of the theatre. I already have a projector mounted on the ceiling for use with a 10' x10 electric screen which is used daily for power point stuff or video showing. It is in the wrong position for my other purposes.

I would love to have a rear projection device of some sort, but dont have enough depth of stage to do that. I have heard of short throw projectors, but I have never seen one.

Has anyone used this sort of device? If so, what approx. image size would you get at what distance? At the moment, I only get shadows cast by actors if they are about 6ft from the back wall. I can imagine it will be difficult to fill this wall with projected images without having shadow problems. It just seems such a useful and simple way to have ready created scenes, or even video (movie) type scenes at the push of a button or two. Any suggestions would be welcome.

John

[Tom]

You can get projectors with a 1:1 lens - so approximately the size of your image will equal the length of your throw.

You'll loose some for keystoning though (I think).

 

You're going to struggle with actor shadows though as you've found and may also find that the intensity suffers at that size - it's the same amount of light output but spread over a larger area.

 

T

[David Lee]

You can get .8 to 1 lens so for example you have a .8m throw you'll get 1m horizontal image. Use good quality lenses for this and shoot from the centre of the lens or you'll get barrelling (where the curvature of the lens will affect the image). You will also lose some intensity with these lenses compared to longer throw lenses. I wouldn't use keystoning adjustment if I could help it, get the projector in the right position if at all possible.

[AHYoung]

When you say short throw projectors youve got 2 choices, the first being a traditional unit with a wide angle lens... this has its own problems as you have to pretty much have the unit lined up with the centre of the screen, if you ceiling mount it the keystone will require a lot of correction, a better option is to use a less wide angle lens with a ration of arounf 1.2 - 1.3 :1 which will allow you to lens shift down and mount on the grid without to much distortion, if you draw the triangles on a bit of paper, the beam of light will fall behind the actors and there wont be too much shadowing as long as the rear of the stage is avoided.

 

an option we have used to make the impossible work is to use a short throw hitachi cpa100

http://www.hitachidigitalmedia.com/product...2&proid=608

this will project from an impossibly close distance, but does rely on the unit being above or below the screen. Its only 2500 lumens but its brighter than youd think , 2 or 3 units will fill the back of a set pretty well as its pretty rare for a stage to be in a 4:3 ratio anyway. they are can be tricky to setup and need a perfectly flat projection surface, but they work when nothing else will { other than sanyo or necs versions...}

 

as an aside Hitachis new range of Event projectors feature a 0.5 ~ 0.6:1 wide angle zoom and it seems to work, sadly allthough their projectors take sanyo lenses, its not the other way round.

 

we have to declare an interest as we rent and sell the things, but the hitachi cpa is well worth a look for the " impossible projection" when ye "cannae bend the laws of physics captain"

 

 

cheers

 

Alastair

[Germaine]

Another very cheap and cheerful option is to bounce your projection of a large mirror therefore artificially creating a greater throw distance.

 

Regards

Germaine

[timtheenchanteruk]

Another very cheap and cheerful option is to bounce your projection of a large mirror therefore artificially creating a greater throw distance.

 

Regards

Germaine

I have dont his as a get out of jail, but dont forget to reverse any text!

[Toxopholist]

Another very cheap and cheerful option is to bounce your projection of a large mirror therefore artificially creating a greater throw distance.

 

Regards

Germaine

I have don't his as a get out of jail, but don't forget to reverse any text!

 

Easily done in most projectors by switching it to its "rear projection" mode

 

Charlie

[AHYoung]

with regard to the mirror, in practice its not as easy for a few reasons, first is to half the distance the mirror has to be half the size of the screen, the other thing is if you go down the ikea / b&q route, youl find the image gets a bit curvy as the mirror wont be anywhere near as flat as you think it is, it also wont be anywhere near as reflective as youd expect either. it can also be interesting rigging a large mirror solidly and at the right angle too.

 

ive done it in the past when you had only 2m to do 3 4m screens, but once was enough...

 

if you want to see a mirror rig that works, have a look at http://www.rearpro.com/products/section2.asp?S2ID=46 the way a small and large mirror work together means large images from a small space. Id still rather not set it up daily though...

 

 

Alastair