Projector Help, large screen short throw

[gafftaper]

Thanks to @LavaASU I have a fantastic used rear projection screen donated to my school. The screen is 18' High by 32' wide. Once mounted on a frame and flown, it will reach down to about a foot off the deck. The ideal location for me to hang it on stage is just behind my mid traveler, 14 feet from the rear wall of my theater. Yeah, that's a really short throw for a 32 foot wide screen.

Assuming there is no projector out there which I can use in that short of a throw, what can I do?

The only idea I have is to mount a projector off to the side of the stage on the back wall aim it toward center then mount a first surface mirror at center and shoot sideways into the mirror. I could have some sort of hinged mount created for the mirror so that it is easy to swing out and locks into the perfect position. When the rear cyc is flown in I have about 2 1/2 feet between the cyc and the rear wall. So there should be enough clearance for a rig to be installed permanently.

Ideas?

 

[BillESC]

How about a hole in your back wall

Even BenQ's PU9730 with the ultra wide lens would require 22'4" to fill your screen.

 

[robartsd]

Thanks to @LavaASU I have a fantastic used rear projection screen donated to my school. The screen is 18' High by 32' wide. Once mounted on a frame and flown, it will reach down to about a foot off the deck. The ideal location for me to hang it on stage is just behind my mid traveler, 14 feet from the rear wall of my theater. Yeah, that's a really short throw for a 32 foot wide screen.

Assuming there is no projector out there which I can use in that short of a throw, what can I do?

The only idea I have is to mount a projector off to the side of the stage on the back wall aim it toward center then mount a first surface mirror at center and shoot sideways into the mirror. I could have some sort of hinged mount created for the mirror so that it is easy to swing out and locks into the perfect position. When the rear cyc is flown in I have about 2 1/2 feet between the cyc and the rear wall. So there should be enough clearance for a rig to be installed permanently.

Ideas?

The first surface mirror would have to be quite large - I think you'd be better off working towards a multiple projector setup or being satisfied with a projected image that doesn't fill the screen (at least the traveler can frame the width).

 

[sk8rsdad]

Panasonic, and likely others, make some large venue projectors with wide angle lens options that can fill the screen. It calls for a 0.38:1 lens which is the widest angle available in that product line.

http://panasonic.net/avc/projector/calculator/html/aspct169/dz870_030_1610.html

 

[gafftaper]

Panasonic, and likely others, make some large venue projectors with wide angle lens options that can fill the screen. It calls for a 0.38:1 lens which is the widest angle available in that product line. http://panasonic.net/avc/projector/calculator/html/aspct169/dz870_030_1610.html

Well that definitely meets my distance from the screen to the back wall restriction. However that lens cheats the throw distance with some extreme keystoning. In order to be placed 12' from the screen it has to be 8' above/below the edge of the screen. Since my screen would end up 1' off the deck, I would have to mount the projector upside down on the back wall 26'+ above the deck... with two electrics, cyc, boarders, etc in the way between that position and the screen, there's no way I can create a clear path for the light from the projector to hit the screen from that position.

How about a hole in your back wall

I have seriously considered that. However the back wall has a lot of pipe and duct work and the other side of that wall is a hallway which is both the stage left/right crossover and the way in and out of the green room. So I would be creating a huge backstage noise issue.

The first surface mirror would have to be quite large - I think you'd be better off working towards a multiple projector setup or being satisfied with a projected image that doesn't fill the screen (at least the traveler can frame the width).

Yeah I'm thinking a multiple projector setup, combined with masking the screen a little smaller is probably the way to go.

 

[LavaASU]

I'd suggest multiple projectors. On the upside you/your kids get to learn blending .

 

[Footer]

Before you go down the multiple projector rabit hole... what is your realistic budget here? What gear do you have already? A switcher that can do edge blending can easily cost as much as a properly sized projector. Also, for a screen that size you are looking at a minimum of a 15k projector... not cheap. Are you married to this screen size? Sounds like you got a free screen that is way to large for what you might need?

 

[AudJ]

As a side, we tested an ultra short throw projector recently. I was hoping to have the ability to move the screen to different lines, as well as avoid shadows if used with actors. There is no good place to project from in our room, as the back wall is blocked with a shell, and the house goes back over 150 ft., requiring an expensive lens. The projector we tested could only get us to about 15 feet wide before we started to see problems. Not quite bright enough yet either. Watching the technology however, as it would be nice to have the projector less than 4 feet from the screen and out if sight.

 

[gafftaper]

Before you go down the multiple projector rabit hole... what is your realistic budget here? What gear do you have already? A switcher that can do edge blending can easily cost as much as a properly sized projector. Also, for a screen that size you are looking at a minimum of a 15k projector... not cheap. Are you married to this screen size? Sounds like you got a free screen that is way to large for what you might need?

I'm in an unusual situation as I will have money to support this project eventually. At the end of the year about 2/3 of the rental money my theater makes gets deposited into my capital improvement/maintenance budget, and I get rented out a lot. Since I have a nearly brand new building I don't need to do any major maintenance or be saving up for new draperies and things like that, so I can afford to spend my money on cool improvements. Depending on how expensive this is it may mean I have to save up for a couple years to complete it, but I imagine I can probably afford to do this in the next 2-3 years.

Am I married to the screen size? Yes and no. If shrinking the screen size down 10% will mean a significant savings (or simply make it physically possible) then I'm willing to do that. But on the other hand if I'm doing this, I'm going to do it right. If that means I have to choose between doing this in 2 years and getting for a 25' wide image or waiting 3 years to get the full 38' wide image, I'm okay with waiting. Fortunately every year i have to wait to do this means that the technology gets cheaper. So that's not a bad thing either.

 

[LavaASU]

I'm in an unusual situation as I will have money to support this project eventually. At the end of the year about 2/3 of the rental money my theater makes gets deposited into my capital improvement/maintenance budget, and I get rented out a lot. Since I have a nearly brand new building I don't need to do any major maintenance or be saving up for new draperies and things like that, so I can afford to spend my money on cool improvements. Depending on how expensive this is it may mean I have to save up for a couple years to complete it, but I imagine I can probably afford to do this in the next 2-3 years.

Am I married to the screen size? Yes and no. If shrinking the screen size down 10% will mean a significant savings (or simply make it physically possible) then I'm willing to do that. But on the other hand if I'm doing this, I'm going to do it right. If that means I have to choose between doing this in 2 years and getting for a 25' wide image or waiting 3 years to get the full 38' wide image, I'm okay with waiting. Fortunately every year i have to wait to do this means that the technology gets cheaper. So that's not a bad thing either.

Also, look at projectors with built in edge blending. That would save a lot of $. I know the larger Christies and Barcos do it, I'm not sure which smaller units do.

Are you allowed to buy used or B stock?

 

[gafftaper]

Are you allowed to buy used or B stock?

On small purchases yes, but this is going to be big enough to require a formal bidding process in which case used/B stock is out.

 

[LavaASU]

On small purchases yes, but this is going to be big enough to require a formal bidding process in which case used/B stock is out.

Whats your anticipated budget like?

 

[gafftaper]

I currently have about $15k I could spend on this. But as I said, I just need to save up for it. I'm assuming I'm going to need a minimum budget in the high $20k to low $30k range to complete this. That's a lot of money, but I can save that up in 2-3 years.

 

[ruinexplorer]

There's no hard and fast rule as to how bright a projector needs to be based on the size of the screen, just what is visible to the audience. A rear screen will offer you the opportunity to have a lower output with the same results. The human eye is most concerned with varying degrees of light to dark as compared to color or resolution. When we use front projection, the projectors need to compete with ambient light much more, ultimately causing us to exponentially have brighter and brighter projectors, especially when not using an actual screen. However, with rear projection, much of the ambient light will spill through the screen, lessening what needs to be compensated for, plus the grey material helps to boost contrast.

There are a couple things to consider when using short throw lenses. You will have less lens shift (if your projector is equipped with it at all) than with a standard lens. The image will likely not have perfectly squared sides due to the optics required. This will be particularly frustrating when blending an image. You also will have much less forgiveness in off-axis alignment. In reality, they don't want to be off-axis at all for your focus and keeping an even field.

Remember that when you are considering the distance, that is from the lens. So when calculating your throw, you need to keep in mind the size of the body of the projector and the space behind it required for proper airflow. In reality, I don't see the plausibility of straight rear projection with even only two projectors. Likely, you will need to use a dual mirror system like this. Even with first surface mirrors, you will lose some brightness.

When I have some more time, I'll see if I can offer you more hard and fast recommendations.

 

[gafftaper]

So a dumb question about edge blending: My screen is 18'x32'. So is the idea that I find three projectors which can do an 18'x10' image, flip them on their side and blend to create an 18'x30' image? That seems really difficult for so many reasons. On the other hand the dual mirror system looks easy to setup and work with. Heck I could make the whole thing portable and run it all from a laptop back stage avoiding the need for any professional installation which would keep the costs down a lot. On the other hand, storage when not in use would SUCK.

 

[LavaASU]

So a dumb question about edge blending: My screen is 18'x32'. So is the idea that I find three projectors which can do an 18'x10' image, flip them on their side and blend to create an 18'x30' image? That seems really difficult for so many reasons. On the other hand the dual mirror system looks easy to setup and work with. Heck I could make the whole thing portable and run it all from a laptop back stage avoiding the need for any professional installation which would keep the costs down a lot. On the other hand, storage when not in use would SUCK.

Nope, the idea is you find 3 projectors, that make a 18 x 13.5 image, filp them on their side and blend to create a 18 x 32 image. With blends, you have to have an overlap area where one image fades out and the other fades in. You do not need a professional installation either way. Keep the system portable so you can do other fun stuff with it if you want (ever seen KA... I know you can't do the live video creation stuff, but you could try using projection as lighting or using video on windows, ect).

I'd look at scaff to put the projectors on. Theres a couple of free programs for blending plus the warpalizer thing I mentioned. Run 5 wire BNC (RGBHV) and you can do long runs if needed or run it from backstage.

 

[ruinexplorer]

Honestly, I wouldn't try for having projectors on their sides. You actually have much fewer options of manufacturers (and models) that allow for it, plus you will get less lamp life doing so. I would instead be trying to make a 24' wide x 18' high image with two projectors, giving you as much blend as you want (up to 25%) and letting the excess bleed into the traveller.

EDIT: You may want to check with your vendors, many of them will deal in B-stock directly from the manufacturer. This way you can get current models for considerably less and have it fit in with bidding.

 

[gafftaper]

I've got some free time so I'm back into looking at this project.

I ran the numbers on the Panasonic ET-D75LE50 lens. It would take a 22.5' throw to fully fill my 18'x32' screen. I've got 14' of space between my rear wall and the screen. If I can use one of these mirror systems like the one below to stretch my 14' throw to up over 20' throw, I should be able to fill most of my screen to full.

So, next question is can I get a projector bright enough to actually handle the task of mostly filling that screen? So my next question for you is how many lux do I need on that screen in order to not have my rear projection screen washed out by a full wash of stage frontlight?

 

[MNicolai]

So my next question for you is how many lux do I need on that screen in order to not have my rear projection screen washed out by a full wash of stage frontlight?

44,300 lumens for a target contrast ratio of 10:1, ambient light of 10fc, and optimistically assuming your screen gain is 1.30. I'm going to bet you don't have $150,000 sitting around for this project though, so best to resign yourself early on to knowing you won't be using this screen for cinema simultaneous to stage lighting anytime soon.

If you are aiming for cinema without stage lighting, then you don't need nearly as many lumens. But throw that stage lighting into the mix and now you've got to ramp up your projector brightness.

Also, whichever lens you pick, you want to be on the wide angle end of it if it's a zoom lens. You can lose upwards of 60% of your lumens by choosing a lens/throw combination that puts your zoom ratio at the narrow end of the lens.

 

[Footer]

I've got some free time so I'm back into looking at this project.

I ran the numbers on the Panasonic ET-D75LE50 lens. It would take a 22.5' throw to fully fill my 18'x32' screen. I've got 14' of space between my rear wall and the screen. If I can use one of these mirror systems like the one below to stretch my 14' throw to up over 20' throw, I should be able to fill most of my screen to full.

So, next question is can I get a projector bright enough to actually handle the task of mostly filling that screen? So my next question for you is how many lux do I need on that screen in order to not have my rear projection screen washed out by a full wash of stage frontlight?

15k for a dark room. If you want to even think about using it while anything else is on your looking at 20k+... and even then your talking about a dim wash or a podium mic type thing. Your going to be looking at a 50,000 dollar plus projector.... and a VERY expensive lens. When you get to these short throw distances it is worth it to take the time to see about front shots.

How often do you see yourself using this system? Do you have the cash to get the proper cabling and switching gear? A good switcher can run 10 grand. You are also looking at a nearly a 1,000 dollar lamp every 3,000 hrs.

Not saying it is not worth it, but really take a look to see if it is. In our space we own a small 5k projector and a 9x12 for doing random things. After that, we rent a system. Our shows vary so much that not one system could cover everything. Screens move, inputs change, and we have to deal with that. It costs about a grand a show but we get the right screen size for what we need, the switchgear needed, and the right lensing for the show.

I'm still in the "you have too big of a screen" camp on this. Who is the actual users of this system going to be most of the time? The renters or the school? If it is the school... go for it. If it is the renters... screw it. Get a hold of a good video vendor and walk them around. Odds are if they know they will get steady work from you they will give you a decent deal for a rental and you can bill it to the client. Everyone wins.