Back Projection Advice Needed

[Eps63]

Hi

 

My little theatre are looking to purchase a short throw projector and cyclorama. Has anybody got any advice and/or suggestions of what type to get.

 

Any information would be valuable. Thanks in advance ?

[sandall]

Welcome to BR, Elspeth. It's hard to give any useful advice without knowing the dimensions of your space, the size of your intended cyclorama (are you thinking cloth or painted back wall?) & what throw-distance is possible..

[gareth]

A few more details will allow much better responses. However, one thing does leap out. If you're looking to do back-projection in the proper sense of the term - that is, the projector is on the upstage side of the projection surface, projecting an image intended to be viewed from the other side - then a regular cyclorama (white filled cloth) is absolutely the wrong thing to be buying. To back-project successfully, the surface you're projecting onto has to be the right medium - do a Google for 'back projection screen' or 'rear projection screen' and you'll see what I mean.

 

(If, on the other hand, you're just talking about projecting a background image onto a white cloth at the back of the stage, with the projector on the same side as the image is being viewed from, then that's a simpler job - but it isn't 'back projection'!)

Edited March 28, 2021 by gareth

[sandall]

If, .... you're just talking about projecting a background image onto a white cloth at the back of the stage, with the projector on the same side as the image is being viewed from, then that's a simpler job

I sort of assumed that the question was really just about projection onto a cyc (which, as you say is fairly simple, at least in concept), but maybe I'm wrong?

[Stuart91]

If you're buying an ultra-short throw projector (with a curved mirror or similar arrangement rather than a conventional lens) then be aware that they need to be positioned quite precisely to fill a screen without distortion. Most models have no zoom and older ones don't have much in the way of keystone correction either.

 

It can be made to work, but may require more bracketry than you might think. And potentially some compromises with lighting, not just in terms of space on a grid but minimising spill onto the cloth.

[Jivemaster]

The blackness needed for good video projection may require changes in your usual lighting plan.

[gareth]

I sort of assumed that the question was really just about projection onto a cyc (which, as you say is fairly simple, at least in concept), but maybe I'm wrong?

 

Title specifically mentions back projection - but that might just be someone not knowing what that actually means...

[pmiller056]

When using a short throw projector, the screen surface must be absolutely flat - a plastered wall is unlikely to be flat enough. A proper suspended projector screen is good, but you may need to secure the bottom corners to stop it moving in draughts (a very small movement will be very obvious). As Stuart notes above, a short throw projector will need to be mounted at the right point in space in front of the screen to work correctly. If you've never used a short throw projector before, borrow and play with one before you commit to buying one for your venue. You will need to take great care in how you light the rest of the stage so that your projected image is not washed out by other lighting. For a given projector, the smaller the projected image, the brighter it will be. If using a projected image as a backdrop, you can make the technical aspects simpler if the bottom edge of the projected image is above actors head-height when they're performing upstage (assuming there's enough space above the actor to the ceiling to show a useful image....) Edited March 29, 2021 by pmiller056

[Stuart91]

It's possible to get "tab-tensioned" roller screens that prevents curling but as Peter suggests a screen that's fixed top and bottom is best.

 

I've had some customers hire short-throw projectors from us, and project onto plaster walls with seemingly good results, but I suspect any lumps or pits in the wall will have an effect on the image.

Edited March 29, 2021 by Stuart91

[sandall]

I've had some customers hire short-throw projectors from us, and project onto plaster walls with seemingly good results, but I suspect any lumps or pits in the wall will have an effect on the image.

I've been to one demo (by a firm charging an arm & a leg to add an amp & speaker to a standard Ricoh) onto an apparently flat church wall. It showed up every blemish in the plaster, but the minister wanted it, so the salesman won the day. No idea if it was ever used in anger. Might be a reasonable solution when there is absolutely nowhere to rig a projector, but far inferior to a "standard" projector rigged above the performance area. Whether back-projection is even practicable for the OP depends on how "little" her "little theatre" is.

[sunray]

Yes if there is one thing that shows up how bumpy a wall is, it is an ultra short throw projector.

 

We installed one in a company foyer to replace a pair of 42" [4x3] plasma screen. I'll guess the image was 80". The wall appeared to be totally flat but what became clearly visible were the screw holes from the screens and a shelf, pair of wall lights and by far the worse the craters where the 6 sockets were.

 

 

I've had some customers hire short-throw projectors from us, and project onto plaster walls with seemingly good results, but I suspect any lumps or pits in the wall will have an effect on the image.

I've been to one demo (by a firm charging an arm & a leg to add an amp & speaker to a standard Ricoh) onto an apparently flat church wall. It showed up every blemish in the plaster, but the minister wanted it, so the salesman won the day. No idea if it was ever used in anger. Might be a reasonable solution when there is absolutely nowhere to rig a projector, but far inferior to a "standard" projector rigged above the performance area. Whether back-projection is even practicable for the OP depends on how "little" her "little theatre" is.

We managed back projection on a 6mx4m screen with a 1.4m projection room but had to use 6 projectors and mirrors. It most definitely did not come under the category of easy. Even now 20 years on I shudder.