Hambone Posted January 15, 2006 Share Posted January 15, 2006 I normally use two projectors and screens, but for smaller venues, can only use one. Stacking two 3500 lumen projectors for 7000 lumens (didn't realize it was an additive process) seems like a good idea. Not only should I get a brighter image on an 8' x 6' screen, but if one fails, the show goes on... What are the issues regarding stacking? As they're both rear-projected from close-range using wide-angle adapters, I thought parallax could make image alignment difficult. I'll have to try it and see. Cooling may be an issue, but having said that, the Optoma EP759s have the hot air ejected from the side. Any experience welcome! Link to comment Share on other sites More sharing options...
Pete McCrea Posted January 15, 2006 Share Posted January 15, 2006 It will give 7000 lumens. It can take a good long while to achieve a good image, and is best done with the machines on a steady platform. The lenses need to be matched and set to the same settings. I've used scaff towers with a platform for each machine, and machines stacked ontop of each other within their rigging/stacking frames. And I'd expect to spend over an hour aligning the image. It is easy to get the centre aligned, but the edges tend to get harder to align, and this leads to a softening of the image- if alignment is out by 1 pixel then the image softens and blurs. Personally I'd only do it where either the client wants the redundancy, or the increased brightness- over 10k Lumens and they can't afford the higher brightness machines. I'd do upto 10k with a machine that offers the required output rather than two of half the brightness. Cooling- as long as the airflow is there then I'd guess it's ok. If you have two machines then I'd go and play and see what results you can achieve. For an image of a double stack click here. The image is quite big (About 1Mb). The Projectors are on the scaff tower at the back of the set :-) Link to comment Share on other sites More sharing options...
Hambone Posted January 15, 2006 Author Share Posted January 15, 2006 That's a pretty cool setup, Pete! The client is me, and I've got to use the two projectors I've got. I may experiment with a very small amount of keystoning, up on the bottom projector and down on the top. The black edges of the screen will hide any artifacts. Sometimes I do abstract and colorful 640 x 480 material, and the fuzziness of poor alignment probably won't matter. It's used more as a lighting enhancement (poor man's LED panel!) than anything else, choreographed with the scanners, laser, color changers, strobes, and blinders. Link to comment Share on other sites More sharing options...
Pete McCrea Posted January 15, 2006 Share Posted January 15, 2006 In that sort of setting it may well enhance the effect your after. When a sharp image is required it can take a long time to get it clean. But with all things if you have the kit, and trying new things doesn't damage it, then play away. After that's where you learn things, get to know your kit better, and discover new ways of doing things. Link to comment Share on other sites More sharing options...
henny Posted January 15, 2006 Share Posted January 15, 2006 one thing not to forget, fire up the projectors up 30min before you try to line them up , things have the habit of expanding and mooving when they warm up. Link to comment Share on other sites More sharing options...
Hambone Posted January 16, 2006 Author Share Posted January 16, 2006 Any links on reasonably priced stacking projector stands in the UK? Link to comment Share on other sites More sharing options...
Andrew C Posted January 16, 2006 Share Posted January 16, 2006 Any links on reasonably priced stacking projector stands in the UK?Not a link to the device as such, but GHAV are selling a second hand Eiki frame for £50. In Winchester though... Link to comment Share on other sites More sharing options...
back_ache Posted January 16, 2006 Share Posted January 16, 2006 It can take a good long while to achieve a good image Is there not any software that can help? I was thinking somthing that could on the one hand output an image similar to the number five on a domino or dice and on the other through to the projectors serial interface, give you a richer interface designed for aligning projectors. If it were really clever it could align it automatically using a camera ! Link to comment Share on other sites More sharing options...
MikeR Posted January 16, 2006 Share Posted January 16, 2006 It can take a good long while to achieve a good image If it were really clever it could align it automatically using a camera ! I seem to recall that a few years back Electrosonic had a gizmo for doing just that, a camera which sat on the front of a video wall and assisted with the cube lineup, though I also seem to recall various people at the time saying that it didnt work. Link to comment Share on other sites More sharing options...
Hambone Posted January 16, 2006 Author Share Posted January 16, 2006 Brainstorming here... As I always use both projectors in exactly the same position relative to the screens (squared up, no keystoning, both lenses on maximum wide-angle, 9' back), why not fasten the projectors to each other with some kind of bracket? Perhaps a thumbscrew method could allow for very small alignment changes. Or even two flat plates connected with long bolts that can be adjusted on each corner for alignment, with a projector on each plate. Link to comment Share on other sites More sharing options...
henny Posted January 16, 2006 Share Posted January 16, 2006 Brainstorming here... As I always use both projectors in exactly the same position relative to the screens (squared up, no keystoning, both lenses on maximum wide-angle, 9' back), why not fasten the projectors to each other with some kind of bracket? Perhaps a thumbscrew method could allow for very small alignment changes. Or even two flat plates connected with long bolts that can be adjusted on each corner for alignment, with a projector on each plate. yep , bolt the projecors to the plates then thredded bar between the plates , that would work, Link to comment Share on other sites More sharing options...
robloxley Posted January 17, 2006 Share Posted January 17, 2006 Depending how big the throw is & how good your eyesight is, a pair of small binoculars comes in handy (a trick from the RGB Barco days) Link to comment Share on other sites More sharing options...
Pete McCrea Posted January 17, 2006 Share Posted January 17, 2006 Brainstorming here... As I always use both projectors in exactly the same position relative to the screens (squared up, no keystoning, both lenses on maximum wide-angle, 9' back), why not fasten the projectors to each other with some kind of bracket? Perhaps a thumbscrew method could allow for very small alignment changes. Or even two flat plates connected with long bolts that can be adjusted on each corner for alignment, with a projector on each plate.That's basically what a stacking frame is. A method to get the projectors securely mounted and maintain their positions, but allow you adjustments, that are potentially mm acurate. The ones that QED, CPS and several others uses is a metal cage that holds the projector, and bolts onto another projector cage. They allow you to align the machines quite well. These also double as flying frames. Link to comment Share on other sites More sharing options...
Hambone Posted January 17, 2006 Author Share Posted January 17, 2006 Can you point me at a reasonbly-priced stacking frame? One that doesn't cost more than my projectors did? - Utterly pointless repeat of the entire previous post removed :o Link to comment Share on other sites More sharing options...
bruce Posted January 18, 2006 Share Posted January 18, 2006 This is bringing back bad memories of spending hours manually aligning the 3 different-colored grids in old-style 3-gun projectors. It was usually easy to do it "roughly", but getting a perfect match was tedious. It's scary to think that those days might not be behind me after all! :o Link to comment Share on other sites More sharing options...
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