Short throw Projector Question

  • Hi all, 

    If anybody has a moment to offer some advice, I'd be grateful.

    I need to buy projectors for a theatre piece and I'm having trouble deciding which route I should go. 

    I'm rear projecting and *trying* to get about a 14 feet tall by 25 feet wide image. I have about ten feet to play with in terms of throw. I've been trying various projectors out on projector central and it looks like long throw projectors in my price range (or probably any price range) won't do it at that distance. So, moving to short throw...I'm just not sure if I move short throw projectors back farther than a couple of feet if the image begins to break up/pixelate/whatever. And I'm not really sure if there are any specs I should be looking at that gives me that information. The calculator on projector central only gives about 2 to 3 feet distance.

    I have about $4000 in budget and figured I'd get two projectors in the 2k range...

    This, perhaps, is a really silly question and I'm sure I'm missing A LOT. But, then again, it will be by far my first silly question on this forum!

  • I've been working with a very similar situation... I only have 11 feet of play back from my projection surface, and need to project 3 separate spaces of 13'h x 11'w. The end result of what I found is that I couldn't do it with projectors in my budget. I had to scale back my size, getting only the 11'w and masking the top with black fabric, which looked a lot like the curtains in the theatre. The projectors I went with were Optoma EH460ST, which cover nicely, have good (enough) four-corner keystoning, and sit at a comfortable 4200 Lumens. Each one cost me, at the time of purchase, somewhere around $1100. I imagine if you were to blend several of them together (Hey, Izzy 3 can do that!), you might be able to take care of that 14' by 25' image just fine.

    You could potentially go with Ultra Short Throw Projectors, but you'll reach a wall (mechanically speaking) where you can't focus the projector properly for the given image size.

    Above all, I have found that the most important part of using rear projections in theatre is to keep the actual lights off of the screen... Even one Source Four aimed at your projection medium and you'll be looking at a white piece of fabric, completely washed out, ESPECIALLY if you stay in the 2000k range. You don't have to spend tons to get something workable, but a brighter projector has almost always served me better than a dimmer one.

    Best of luck!

  • Tech Staff

    In order to achieve the image size you need at the throw distance you have, you need a 0.35:1 lens. This is an ultra short throw projector.

    At the image size you require, you need about 10,000 lumens to have a bright enough image, under typical theatrical lighting conditions. If your show is relatively dark, you might be able to get away with ~7000 lumens.

    As long as the projector is correctly aligned to the surface, focus and pixilation are unlikely to be a major issue.

    An alternative would be to use four projectors with a 0.72:1 lens, with each unit having around ~3000 lumens. Each projector would do 1 quarter of the total screen space. You'd then need to do some edge blending, fortunately this is much easier with Isadora 3 but will still require a lot more work.

  • @mc_monte Thanks! That's roundabout what I thought, without the actual numbers. I'm sort of between a rock and a hard place. Can't afford four new projectors or, probably, an UST that's that bright (although, honestly, I can't even seem to find one online). Plus, I'm not sure if UST will be useful for other projects in the long run, so is it worth the investment. So, I guess I'll need to weigh my options and try to figure out the middle ground... Very much appreciate your help. 

  • @rbecker Great to hear your experience. Between this and the comment below, it gave me a lot to think about. I probably can't arrive at the perfect solution, but I can come up with something.

  • I use old BenQ 776ST's for this (I bought them in 2009 and they're still going strong!), which at 3500 lumens I would blend together to do what you want. They have  a .6 lens, but are only 1024x768 resolution. I also have 10K Panasonic projectors, which are awesome, and they make a fabulous .39 lens for them. BIG bucks, though. The Optima's suggested above sound very promising. I would love projectors with .5 lenses! They're also HD. Having said all of that, I hope to never buy another projector (I have about 10) unless it's laser: it's the only sensible modern choice.



  • @citizenjoe said:

    unless it's laser: it's the only sensible modern choice

     Amen to that!!

  • Tech Staff

    I have been working a show that uses 3 rear projection show throws with about 10ft depth.
    In this case I have 3 side by side screens, so I haven't needed to blend.
    I have the center unit hitting 16x10 ft (if I remember exactly, the 2 sides are 14x10).. giving me a 44ft x 10ft screen.
    It could be brighter, but doesn't look bad.
    I used these 3500 lumen projectors

    Pics, to get a sense of brightness.