Film-Tech Forum ARCHIVE: Extreme short throw projector

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Posted by Geoffrey Hudson (Member # 7456) on 02-05-2013, 02:52 PM:

Hello. I'm new to the forums. I must say I was pretty pleased to find this by accident. It seems a great resource for talking the nuts and bolts of theater operation! I work at Wealthy Theater, a 100 year old venue in Grand Rapids, MI.

Anyway, I had a projector question to put out here and see if any of you more experienced types might offer any feedback.

What we are trying to do is mount a projector from a lighting truss onstage to project on the cloth at the rear of the stage.... We're not exclusively a movie venue, people use the space for many things and sometimes we have need for this type of projection...

So we are talking about a throw distance of only 10' filling a visible space about 12' x 30.'

I've looked at a few extreme short throw projectors and am leaning towards the NEC NP-UM330W:
http://www.bhphotovideo.com/c/product/906909-REG/nec_np_um330w_np_u330w_lcd_wxga_3300.html

Does this seem like it would do the job or can somebody suggest a more suitable model? Any factors I haven't thought of?
I see the lenses on these short throw are noticeably different. So they'd hopefully be equipped for some Xtreme keystoning?

Any help is appreciated!

Posted by Carsten Kurz (Member # 5396) on 02-05-2013, 03:04 PM:

What kind of projector would you use? Will it have to play regular cinema content under the same conditions as well?

- Carsten

Posted by Geoffrey Hudson (Member # 7456) on 02-05-2013, 03:26 PM:

That NEC projector I mentioned was the one I am considering. Looking to get advice if I am on the right track.

Our stage has a screen that lowers at the front for cinema content.
We raise it to use the stage for live performance.
Sometimes there is a need for logos, powerpoint or video as accompaniment to be projected in the background during performances.
We have been using our main projector for this but it isn't ideal as we are coming from 70 feet away and are projecting onto the performers.
The idea with this 2nd projector is to put it on the lighting truss of the stage and project overhead onto the back of the stage.
Hopefully my explanation is clear. Maybe should have made a diagram...

Posted by Richard Fowler (Member # 893) on 02-05-2013, 03:59 PM:

I have used this type of projector for advertising (rear screen) in hotel lobbies and front screen for stage "video scenery". The trade off is fairly limited postioning of image to screen due to the lens designed to project at a 50 degree angle. Your 12 x 30 cyc would need three of these to cover the area widthwise.....get the lens chart and dimensional drawings and work up a shop drawing or rent one to check your space.

Posted by John Thomas (Member # 6509) on 02-05-2013, 04:51 PM:

Is rear projection out of the question?

Posted by Geoffrey Hudson (Member # 7456) on 02-05-2013, 05:10 PM:

We are trying to project onto the cyclorama which is only inches from the stage back wall so rear isn't really an option.

Posted by Mike Blakesley (Member # 26) on 02-05-2013, 11:42 PM:

What about keystoning? You're projecting at a huge angle. Can a digital machine adjust for THAT much of an angle?

You could have a guy like our own Bobby Henderson in the crowd who would be very upset if his carefully designed logo was projected all distorted.

Posted by Cameron Glendinning (Member # 3516) on 02-06-2013, 01:27 AM:

I use short throw 720p wxga projectors for outdoor cinema all the time. They have a fixed lens so positioning is not flexable and the projector MUST be exactly in the center (near the top or bottom of the screen) or noticeable distortion is obvious. Optoma have 3 short throw models available with 0.3, 0.52 or 0.7 options. 1 being the width of the screen. 3100 lumen s will just fill a 25 x 14ft screen in darkness with a reasonable quality of brightness.

Your cloth is not the native shape for most computer or HD video and needs a more realistic 16.9 ratio, which would be closer to 20x11ft. If your lighting truss is close to the top of the "screen" the image will not need much keystone correction.

With a 0.52 lens with a 10ft throw, you will produce a image close to 20ft wide image that's about 11 ft tall when keystone is set correctly. Computer images can be a bit taller than a dvd. 16.10 ratio

With the smaller image depending on the screen/ cloth and its gain you will have some extra brightness which will help with ambient light.

Different settings in the menu dictate the real lumen output, usually movie is the darkest, presentation the brightest.

Posted by Carsten Kurz (Member # 5396) on 02-06-2013, 07:29 AM:

30' wide with a 3300lm projector would probably be enough for non-cinema content in a dark auditorium.

Under stage light conditions, it is definitly not enough. You should go towards something above 5000-6000 lumens.

Very often, dedicated short throw projectors have no lens shift. With 10% keystone correction like on the NEC, that could be insufficent. Plus - with a large amount of electronic keystone correction, you not only lose image quality, but also light (in the corrected corners).

Not a good idea. Look for projectors WITH lens shift., and optional wide angle lenses (and check wether lens shift can be used with that lens at all).

Is there a tight budget for this? At 1.300US$, your options are very limited.

- Carsten

Posted by Richard Fowler (Member # 893) on 02-06-2013, 09:06 AM:

Depending on the set or lighting designer intent of effect you need enough lumens to counteract light spill / floor reflections. The smallest unit I use is 8000 lumen and have done stacked and blended displays at 24000 - 30000 lumen for a full stage treatment. 3300 lumen may be fine in your situation....best to do a mock up to see if you are satisfied. If your cyc is cloth more light is need versus a white PVC sheet. Recently we are getting more request to hang mini video projectors on electrical flylines for video effects on floors and set walls + cameras to catch a overhead view for dance companies.

Posted by Geoffrey Hudson (Member # 7456) on 02-06-2013, 11:28 AM:

Thanks for all the great info everyone! Quite a few aspects I hadn't thought of.

We are not necessarily locked into a $1200 budget for this projector but wouldn't want to go much over say $1500.
This is a secondary use projector for special onstage situations. We are shopping for this in addition to a new main cinema projector (possibly a Solaria One) so the bulk of our budget will go to that and what's left for this onstage projector.

There are probably a few projectors or lenses that might do what we're looking for but there are so many options out there I don't even know how to narrow it down...
Was hoping somebody might chime in with something like "Oh yeah, we do exactly what you're trying to do! We use a _______ and it works great for us!" [Wink]

Posted by Scott Norwood (Member # 30) on 02-06-2013, 12:23 PM:

Is there a reason why you con't use your normal video projector, perhaps with a different lens? Is it an issue of a steep throw angle from the booth or something like that?

Posted by Geoffrey Hudson (Member # 7456) on 02-06-2013, 12:25 PM:

The issue with using our main projector is that you end up projecting on top of performers on the stage. The thought with having this secondary projector on the lighting truss is that then we're projecting over them.

Posted by Carsten Kurz (Member # 5396) on 02-06-2013, 04:53 PM:

There is a site in german which allows you to search all current and previous projectors on the market by various aspects like brighness, projection geometry, etc.

That could reduce the enormous amount of projectors available to the few that may be of interest for you.

But I think you need to measure the stage very well and make a drawing of projection distance, image width, projection offset. And try to relax your constraints.

http://www.projektoren-datenbank.com/menu1/menue/sucheingabeprojektor.php?menue=22

Funny, when I feed a projection ratio of 0.3 to the search engine, it comes up with 41 hits - all with rear-projection mirrors, so bascially, all whiteboard projectors.

0.3 and a tight budget - nearly impossible. You should first try to rent one to see wether it is working at all.

- Carsten

Posted by Jay Glaus (Member # 6011) on 02-09-2013, 03:04 AM:

Don't know if this helps, and I'm fairly new to the digital end of projection, but didn't Barco just come out with a very small scale projector? Don't know if it would work or not and never priced it out.
Jay

Posted by Geoffrey Hudson (Member # 7456) on 02-09-2013, 10:27 AM:

Hmmm... I'll check into the Barco. It'd be interesting if they did have something like that because it was a Barco rep who'd actually suggested the NEC short-throw that I was considering...

Posted by Carsten Kurz (Member # 5396) on 02-09-2013, 10:29 AM:

As this is a digital cinema forum, Jay probably thought about the new Barco DP2k-10Sx.

That, however, is a DCI machine. It has no specific wide-angle lenses, nor does it fit your budget for this stage projector application. It is a similiar machine to the Solaria One.

- Carsten

Posted by Cameron Glendinning (Member # 3516) on 02-09-2013, 07:03 PM:

To use a 0.3 and a typical computer or tv image you would need a 18 ft tall screen. These projectors have no zoom. 0.5 would give you an image that does not spill onto the roof and the stage floor. Unless you plan to run dvd's of cinemascope films ONLY!

Posted by Geoffrey Hudson (Member # 7456) on 02-09-2013, 10:07 PM:

Is it just that it's not possible to do what I am trying to do with any equipment that currently exists? Starting to sound that way. [Smile]

Posted by Carsten Kurz (Member # 5396) on 02-10-2013, 09:48 AM:

You will definitly see a picture, but probably too dim in typical situations. As I said, make a scale drawing, consider all options for mounting the projector.

If the pieces to be performed offer decent control of stage lighting, it may work.

I used to do video projection for theater pieces with 1000 lumen beamers, but at the time, it was so evident that the lights would have to come down during projection, that no one really questioned it, so the piece and lighting was tailored to the projection.

Sure you can have a try - I still would try to rent such a projector first to test it.

I have never seen an image projected with a 0.3 projection ratio. It doesn't have to be that bad, and it is not intended to show any cinematic brilliance, just to have some punch.

All these projectors seem to work with a mirror. Datasheets typically quote small projection sizes - like 100" max. Not necessarily a physical limit, but as I already wrote, these are typically whiteboard projectors, not intended for large screens, and they certainly have more constraints than general use projectors.

There is e.g. the Epson EB- 485W with a projection ratio of 0,27:1. It is LCD, though. I think for a stage situation, DLPs in that price range would deliver more punch than LCDs. Make sure you can return the unit if your test shows you can not focus the image within your chosen geometry. This is usually never a problem with standard projectors, but these special short throw units could have real limits in screen/focus distance and thus max. image size.

- Carsten

Posted by Cameron Glendinning (Member # 3516) on 02-10-2013, 11:05 PM:

I've seen 0.3 projectors, infact I was asked to review one some time ago. But in your case an 0.5 is what I would be using.
video review

Posted by Jonathan Bodge (Member # 4072) on 02-11-2013, 08:05 PM:

If you have fly space project down on a mylar mirror.

Posted by Jonathan Bodge (Member # 4072) on 02-12-2013, 11:40 AM:

Unfortunately the mylar mirror would be quite large for a 16/9 image at a 10 foot throw w/ a .67 lens, and quite expensive.