# Rear Projection



## productionmgr (Dec 30, 2010)

My Producer has given me the task of finding out all of the information needed for a rear projection system in our theatre. He wants to be able to rear project full sized drops (18x40). I know nothing about projection systems and I was wondering what type of lens I should be looking for to produce such a large picture. I know that I'm going to end up with two lenses because he also wants to use it for the smaller scale youth shows that we do. Any assistance is much appreciated.


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## shiben (Dec 30, 2010)

Ok. Multiple things to think about. How long is your throw? If its short, can you get together multiple smaller projectors and network them all with Watchout or a media server of some sort? What material will you be trying to project through? Having multiple RP screens is going to cost a bundle. You cant just grab a piece of muslin cyc material and expect it to function as a good projection screen. You cant have any seams, and most material is not uniformly diffused, so you will need to consider cost of the screens higher than the cost of a normal soft good drop. If you want to paint on it, count on the bean counters flipping. Also, you dont necessarily need 2 different lenses, especially if its more practical to use an array of projectors rather than just one. Now, a big 20k projector will nicely project on a screen of that size, but expect to pay loads of money for it, and also expect to have to run special power (i think our arena has 20ks with 30A? circuits to them). You then need to think of price, and you cant just say "I can afford to go to x price". You need to consider the punch you need. Our 20ks nicely punch on slightly smaller screens through game HIDs in an arena. Not sure how lights pointed at the screen will change this situation, but something to think about. Another thing to consider, 18x40 is not a standard aspect ratio, so you'll need to customize your images to fit in a standard aspect ratio and then trim the excess wash with opaque masking. You will also need to consider a shutter system, although I cant imagine this not being included in a very high end projector. Also consider your control, if you put 20,000 into a projector, a few thousand more into the lens, and who knows how much into a drop to project on, youll probably want to use it for a lot of stuff, so media servers and whatnot are going to be wanted, if not needed. Look at Isadora, Catalyst, Green Hippo and Axon for a few common ones. If you choose to use many smaller projectors, Watchout is what I have seen used a lot to stitch all the images together, and that is a very expensive system. Even if you choose to just use one large projector, for theatrical grade projections, powerpoint is not going to cut it. Consider using Qlab or its windows based equivalents. Actually, Qlab might be able to deal with the stitching of all the projectors together, but Im not sure. Another critical thing that your producer has possibly not considered is that having projection in the show requires hiring an additional designer, an additional technician for the run, and a couple of people to tech the system. Also, projection is a lot more than finding images online and sticking them on a screen. At 18x40 feet, what looks good on your 1024 13" macbook looks like crap in 1080P on a 43 foot screen. You need to generate a lot of your own content, and consider that everyone can see the entire image very well. Also, CNN or someone did a youtube debate last election cycle, tried to put the youtube quality images up on a video wall, looked like crap. Consider that. So if you want to make a video, get ready to buy or rent a HD digital video camera every time you need to use it, along with a software suite to edit it down. I have used iMovie, but it was a bit rough. Wish I had finalcut pro. So youll need to have a designer, probably a graphic artist or content creative person in there as well as your running technician. 

All this to say, your system is going to be specific for you. Obviously, Im thinking you want a real projection system, useful for showing movies and use during theatre. If you just want to run slideshows, this is a different issue altogether, but still has some of the same issues involved, such as powerpoint not making good pictures, and probably needing a switcher. You need to decide what exactly you want to do, and then get distances from your back wall/projection position to the drop, an exact drop size, and other relevant dimensions. These will decide what type of lens you need to buy. Then, Decide how bright it needs to be, possibly demo a system to see how it works?


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## museav (Dec 30, 2010)

shiben said:


> Now, a big 20k projector will nicely project on a screen of that size, but expect to pay loads of money for it, and also expect to have to run special power (i think our arena has 20ks with 30A? circuits to them). A year or two ago we were looking at these and the rule of thumb was a dollar per lumen. This seems like an inconsequential issue, just get the size you can afford, but then you have to consider if there will be light on the front of the drop, which will make it harder to punch through (although RP is better than front, in my experience). Our 20ks nicely punch on slightly smaller screens through game HIDs in an arena. Not sure how lights pointed at the screen will change this situation, but something to think about.


You brought up numerous very good points but I have to question the pricing comments. 20,000 lumen projectors are pretty much limited to some Barco, Christie and Digital Projection products and a quick look at pricing for those models shows list prices of $70,000 or more plus the cost of the lens. I also wouldn't expect the actual cost to be as much below the list price as it is for many higher volume products.


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## ruinexplorer (Dec 30, 2010)

I agree with Brad. If you are looking around a dollar per lumen, you are looking at LCD projectors for boardroom use (5000 lumens and below). 

productionmgr, I would recomend, if you have not already done so, to use the search function on many of the points that shiben mentioned. You may find much of the information that you need to discuss the matter further with your producer and then be able to have the understanding you need to get further direction. If you need help with the search function, send me a PM and I'll get you on your way.


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## shiben (Dec 30, 2010)

museav said:


> You brought up numerous very good points but I have to question the pricing comments. 20,000 lumen projectors are pretty much limited to some Barco, Christie and Digital Projection products and a quick look at pricing for those models shows list prices of $70,000 or more plus the cost of the lens. I also wouldn't expect the actual cost to be as much below the list price as it is for many higher volume products.


 
Im not in the purchasing department for our school, so I stand corrected. This was just the rule of thumb someone in the department mentioned when we were installing control lines for our projectors. You are more experienced with the price end of things (I just make pretty pictures to go on them and plug them in). Ill edit my original post.


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## museav (Jan 1, 2011)

The pricing is definitely a volume issue, as ruinexplorer noted the dollar per lumen, or even less in some cases, may hold true for typical classroom and conference room projectors but when you get to large venue or special application projectors things can change. This is unfortunately a common issue where schools look at what they spend for a classroom projector and assume a projector for an auditorium or theatre would be just a bit more. They also tend to look at going from one diagonal screen size to one twice as large as thus requiring twice as much brightness when in fact a doubling of the diagonal, height or width dimension represents a quadrupling of the area and thus requires four times as much output from the projector to provide the same image brightness.


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