mk_193 Posted March 10, 2014 Share Posted March 10, 2014 Hi, I'm trying to help someone figure out how to set up a projection system to be used as part of 1hr live performance. What's the best way to set up back projection? I've seen suggestions using mirrors. Also they have no screens to use- what else can be used to project on? Thanks! Link to comment Share on other sites More sharing options...
top-cat Posted March 10, 2014 Share Posted March 10, 2014 Mirrors? To do rear projection you simply put the projector behind the screen, rather than in front of it (hence rear). So the audience is looking at the image through the projection surface, rather than a reflection off the projection surface. If you don't have a proper projection screen, you may find rear projection difficult since any fabric etc that you might use may be too opaque to let light through it, so you would need a more powerful projector to achieve the same results. White fabrics etc can also behave strangely with colours. The other big thing to bear in mind with rear projection is that you need sufficient space behind the projection surface. That, IME, is the main thing that stops people using rear projection in many live performance scenarios. There is simply not enough space behind the screen to fit a projector and the space it needs to focus on the surface. Link to comment Share on other sites More sharing options...
Shez Posted March 10, 2014 Share Posted March 10, 2014 Mirrors aren't uncommon where there is limited space behind the screen - I recall a tour where the projector was flown pointing downwards and bounced off a large 45 degree mirror. This of course relies on using a projector that can be used in that orientation and having a suitable front-silvered mirror. Not something to be attempted by beginners of course! A search will likely turn up many suggestions of materials to use for rear projection surfaces but your best results will always be achieved by using the right material. Is hiring a fastfold or similar screen an option? A projector with a wide lens (short-ish throw) will minimise the amount of space you need behind the screen but is more likely to give you a hot spot in the middle. Note that short throw projectors (the ones that use mirrors to project at a very steep angle) may seem attractive is space is very limited but they don't work well on a screen that is not completely rigid. Link to comment Share on other sites More sharing options...
kitlane Posted March 10, 2014 Share Posted March 10, 2014 I've actually had some good results with various materials for rear projection. One of the best was a thin sheet of foam used in packaging. You do need to experiment though. As TC states, the colours may be all over the shop. Also, look out for the hot-spot of the projector and the viewing angle. As for mirrors, I suggest you forget they even exist until all other avenues have been explored. To get the best quality image you need an expensive front-silvered mirror. The main problem, though, is that the mirror usually has to be really big. Here is an over-simplified example. Let's say you have a 1:1 lens (which you probably won't). A 5m throw distance will give you a 5m wide image. If you only have 2.5m throw distance you could use a mirror to double it, but the mirror will have to be 2.5m wide. Link to comment Share on other sites More sharing options...
top-cat Posted March 10, 2014 Share Posted March 10, 2014 Mirrors aren't uncommon where there is limited space behind the screen - I recall a tour where the projector was flown pointing downwards and bounced off a large 45 degree mirror. This of course relies on using a projector that can be used in that orientation and having a suitable front-silvered mirror. Not something to be attempted by beginners of course! Are you in fact thinking of Musion projections? Musion make holographic projections using a downwards facing projection, bounced off a screen on the floor, onto a 45 degree film; to create what appears to be a 3D hologram in front of a stage? Very clever stuff, definitely not beginner zone material; and also a very expensive and very bright Barco. Link to comment Share on other sites More sharing options...
timsabre Posted March 10, 2014 Share Posted March 10, 2014 You can often get away with normal mirror rather than front silvered mirror, you do get slight image ghosting but unless you are projecting computer desktops or very fine graphics it is not very noticeable.However it is very true that the mirror needs to be BIG, and it also needs to be very flat. If there is any distortion in the flatness of the mirror there is twice as much distortion in the image. Link to comment Share on other sites More sharing options...
Shez Posted March 10, 2014 Share Posted March 10, 2014 Are you in fact thinking of Musion projections? Musion make holographic projections using a downwards facing projection, bounced off a screen on the floor, onto a 45 degree film; to create what appears to be a 3D hologram in front of a stage? Very clever stuff, definitely not beginner zone material; and also a very expensive and very bright Barco.No, just a standard theatre tour but the screen was the the full width / height of the set at the back which would have needed rather too great a throw for most venues. Link to comment Share on other sites More sharing options...
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